The Alaisiagae were Celtic deities and Germanic deities who were worshipped in Roman Britain, altar-stones raised to them having been recovered in the United Kingdom at Vercovicium (Housesteads Roman Fort) at Hadrian's Wall in England.
Another centre of worship was perhaps the town of Bitburg, near the German-Belgian border, which was called “Beda Vicus,” which although Latin derives from the Celtic "Village of Beda.".
One of the votive inscriptions to these goddesses reads:
Mars Thincsus is thought to be the Germanic war-god Tiw who was also connected to oath-taking and the thing, a kind of judicial gathering. Scherer suggests that they came from the district of Twenthe (hence, the mention to "cives Tvihantis") in the province of Over-Yssel, Holland.
The second inscription reads:
These goddesses are possibly recorded on two inscriptions in Greek recorded in l'Année Épigraphique for 1973.
The goddesses called the Alaisiagae are named on altar-stones from the same fort on Hadrian's Wall as being parallel with two Germanic goddesses: Celtic Boudihillia is equated with Germanic Fimmilena and Celtic Beda is equated with Germanic Friagabis. These parallel goddesses are taken to be Germanic not only because of clues in the inscriptions and the Germanic mercenaries at the wall at the time, but also because they both have an initial ‘f-,’ a sound not known to have developed in Celtic at this time. Equally, the two goddesses are not known to be Roman. Beda may have been an abbreviation for Ricagambeda since the two names share similar semantics. Boudihillia and Beda are more likely Celtic names however.
The altar stones of the Alaisiagae were recovered in the Temple of Mars at Vercovicium. This roughly circular temple was found on top of Chapel Hill a little to the south of the fort, its walls of undressed stone facing with an earth and rubble infill enclosed an area measuring about 17¼ ft. across. The insubstantial foundations indicate that the superstructure was at least half-timbered.
The temple was built in the early-3rd century upon the ruins of a rectangular workshop in the vicus which had been destroyed during the barbarian incursions of AD196. It contained altars dedicated by the commanders and men of all three units known to be stationed at Vercovicium to the god Mars Thincsus, the Romanized aspect of a Teutonic god, a common occurrence among the Roman auxiliary units. Various altars have been found at this site dedicated to Mars and/or to the Celto-Germanic goddesses Alaisiagae; named on one altar as Beda and Fimmilena, on another as Boudihillia and Friagabis.
Boudihillia can be derived from the Proto-Celtic *Bōud-ī-hīlījā meaning 'victory’s fullness.' Beda is derived from the Proto-Celtic *Bed-ā meaning 'burial.' Alaisiagae is derived from the Proto-Celtic *Ad-lājsījā-agai meaning (in the illative) 'sending fears,' plausibly a byword for a notion of “dispatching terrors” (q.v.   ).