Laetitia is the Roman Goddess of joy, gaiety, and celebration, and is especially linked with holidays and festivals. Like many Goddesses Who were personified ideas, Laetitia seems to have been a late addition to the Roman pantheon, and was often found on coins of the Empire, used for propaganda purposes to boost the image of the Emperor or his family. Her name means "Delight", "Happiness", or "Joy", and could additionally be defined as the "Fruitfulness" or "Fertility" assumed to be the foundation of that happiness. Her name is related to the Latin word laetus, which has a whole cluster of meanings connecting happiness with prosperity and abundance: it can mean "happy", "glad", "lucky", "successful", "prosperous", "luxurious", "lush", or "abounding"; and it was used to describe fertile land.
Laetitia is depicted on the coins of several Emperors of the 2nd and 3rd centuries CE, and can bear a variety of attributes; She is often shown holding or wearing a wreath or garland as a symbol of celebration, since wreaths of flowers or leaves were commonly worn during festivities or holy rituals. Likewise She can be shown with a branch of greenery, as they were used for some holiday decorations (much like we "deck the halls with boughs of holly" for Christmas or Yule—which tradition, incidentally, owes a lot to the Roman Saturnalia). She may carry symbols of fertility and prosperity such as apples or a handful of wheat sheaves; or symbols of power such as a sceptre or spear; She was sometimes shown with an anchor, as a representation of stability, or, like Fortuna, a ship's rudder symbolizing guiding fortune or the actions chosen to steer one towards prosperity.
Laetitia was given several epithets depending on the type of joy the Emperor was attempting to take credit for bringing to the Empire. On coins of the Emperors Gordian III and Gallienus, who both reigned in the mid 3rd century CE, She is Laetitia Augusta, "the Joy of the Emperor", which, in propaganda-style, can be taken to mean "the joy the Emperor brings to the people", though it may also have been a way of announcing the birth of a child into the imperial family. On these She is shown standing in Her typical pose, with a garland in one hand and an anchor supporting the other; other coins labelled Laetitia Augusta depict a ship with the Emperor himself steering it, reinforcing the idea of the Emperor as the one who brings happiness to the people of the Empire, though it likely also refers to the idea of prosperity through naval conquest and the control of the resources of the conquered.
She could be known as Laetitia Fundata, "Established" or "Well-Founded" Joy; these coins usually show Her with a ship's rudder, often resting on a globe. Again, these depictions hammer home the idea that the foundation of the Empire's happiness was built on its ability to dominate and direct the course of events, though they may also, more practically, make reference to the Empire's dependence on imported grain to keep its people fed. As Laetitia Fundata She was featured on coins of the Empress Crispina, the wife of the notorious Commodus (who you may remember from the movie Gladiator; he was killed by Russell Crowe) and of the Emperor Philip I; one wonders though if the wishes for a secure and stable variety of joy were a result of their own insecure times—for Philip I was killed in battle alongside his son Philip II, and Crispina, well, she was banished from Rome, only to be murdered. (Ten years later, of course, Commodus himself—on whom my otherwise comprehensive Classical Handbook wastes a single line, calling him "the worthless son of Marcus Aurelius"—was murdered, on the very last day of the year 192 CE. Felix sit annus novus, indeed!)
On a coin of the Emperor Antoninus Pius, who ruled 138-161 CE, the inscription on the back side refers to Laetitia and to his 4th consulship (a consul being roughly a co-president of Rome, an office which, in the oh-so-democratic world of the Roman Empire, could be held by the Emperor at the same time he was Emperor&—yeah, real big on the separation of powers there); though its hard to say if it refers to the Goddess of joy or just joy as a concept since She is not depicted on it; rather the grain Goddess Ceres is shown with Her daughter Proserpina (perhaps better known by their Greek equivalents Demeter and Kore or Persephone). Ceres holds wheat sheaves while Proserpina holds a pomegranate; though both are proper to those Goddesses, they are also similar to Laetitia's attributes of fruit and wheat as symbols of fertility and prosperity. In the case of Antoninus Pius, the mother-daughter divine pair probably makes reference to his devotion to the Emperor Hadrian (hence the "Pius" surname), who had adopted Antoninus as his heir.
The Joy-Goddess also made appearances on coins as Laetitia Publicae, "the Joy of the People" or "the Common Joy", again implying that the Emperor is the cause for the populace's (hopefully) current prosperity. As other depictions She holds several ears of wheat in Her right hand; but in Her left She holds the hasta pura, literally a "blameless spear", a special type of small spear missing the iron blade which was given as a military award, generally to a soldier who had saved another's life. As a symbol of divine power the hasta pura was also carried by the Goddesses Pax ("Peace") and Providentia ("Providence" or "Foresight"), perhaps to indicate righteous victory, or the peace and prosperity that can flourish when a war is won.
And lastly, She was on some coins called Laetitia Temporum ("Celebration of the [special, rare] Occasion"); these coins, too, did not generally show the Goddess Herself, but had an image of a boat surrounded by wild animals. This referred to the great public spectacles of the ludi saeculares, or the Saecular Games, so-called because there were supposed to be held once in a saeculum, meaning an "age" or a "century", making them literally "once in a lifetime", though unsurprisingly they weren't held with quite that regularity. The ship surrounded by animals may represent the importation of exotic animals to be killed for sport in an amphitheatre, or it may be a depiction of a mock "battle" with the said doomed animals. These ludi saeculares were primarily dedicated to the King and Queen of the Underworld, Dis and the above-mentioned Proserpina, in thanks for or in the hope of averting plague; and their importance and extravagant nature were due to being established to assure the future health and continuity of the Roman people. According to one tradition they were founded in gratitude when a disease afflicting children was lifted; another says they were first held to appease the angry Underworld Deities, who had sent a terrible plague which caused every unborn child to die in the womb. Historically the ludi saeculares were reserved for when dire emergencies threatened Rome, though the Emperor Philip I held them in 248 CE to mark the millennial celebration of the city.
As was appropriate to a celebration on such a grand scale, many of the Gods of the Roman pantheon were invoked at the games; and though Laetitia is not referred to by name, Her mention on the coins minted to commemorate the event does seem to imply that She was considered some sort of patron Deity of the games, or was at least thought to be the personification of celebration on such a grand scale. And as the ludi saeculares were specifically concerned with the fertility of women and the birth rate, Laetitia's connections with fruitfulness as well as happiness would be quite appropriate. It is interesting to note, also, that the festivities of the ludi saeculares were in reaction to a real and very dark fear, much as midwinter festivals like Yule and Christmas are based in the hopes of light driving away the dark; perhaps Laetitia then more accurately represents the ability to celebrate and be joyous in spite of one's fears.
Laetitia, or more accurately, a "groundless" version of Her is mentioned by Ovid in his Metamorphoses as being a friend of the Rumor-Goddess Fama; in this case, Laetitia represents the unfounded joy gossip can quickly bring and just as quickly dash.