ribadyan is the Westron word for a person celebrating his or her birthday.
 Hobbit customs
Birthdays had considerable social importance for the Hobbits, and customs were regulated by fairly strict etiquette, usually reduced to formalities.
The Hobbits generally exchanged gifts as a form of "payment" for services but also of thanksgiving in favors and friendships. According to an ancient custom, a hobbit baby, shortly after birth and its name-announcement, was given a gift by the head of the family, as a token of accepting it into the family (on the rare cases of adoptions, parents gave gifts to their new child). Gifts then became a means of recognizing family membership, and the head of the family ritually gave something, even if only a token, to a birthday celebrant.
On its third birthday, a hobbit child gave presents to their parents, that typically was something that was personally found, or produced (made or grown). This may have been extended to other ages and relatives, and began the custom of the celebrant also giving something to the persons of their environment along with the older and most formalized custom of receiving.
The present given by the celebrant was typically something owned or produced by themselves; as a rule something not very expensive, but its nature depended on time, places, the age and status of the celebrant. The head of a Shire house would distirbute gifts to all residents, servants, neighbors and others; and commonly giving a party, distributing presents to all invited. In the Shire of Bilbo's time the recipients included near kin and neighbors ("twelve-mile cousins"). Withholding an expected gift was taken as a rebuke. The giving was made in person and privately, avoiding embarassments; properly before the birthday, the latest being the nuncheon on the birthday.
 Other versions of the legendarium
Many details of the gift-exchanging customs come from a draft of a letter Tolkien wrote. In that letter Tolkien mentions that he considered putting such details into the Prologue but that would make it too long and overloaded according to some critics.