Gaius Valerius Troucillus

Gaius Valerius Troucillus or Procillus ( mid-1st century BC) was a Helvian Celt who served as an interpreter and envoy for Julius Caesar in the first year of the Gallic Wars. Troucillus was a second-generation Roman citizen, and is one of the few ethnic Celts who can be identified both as a citizen and by affiliation with a Celtic polity. His father, Caburus, and a brother are named in Book 7 of Caesar's Bellum Gallicum as defenders of Helvian territory against a force sent by Vercingetorix in 52 BC. Troucillus plays a role in two episodes from the first book of Caesar's war commentaries (58 BC), as an interpreter for the druid Diviciacus and as an envoy to the Suebian king Ariovistus, who accuses him of spying and has him thrown in chains.

Troucillus was an exact contemporary of two other notable Transalpine Gauls: the Vocontian father of the historian Pompeius Trogus, who was a high-level administrator on Caesar's staff; and Varro Atacinus, the earliest Transalpiner to acquire a literary reputation in Rome as a Latin poet. Their ability as well-educated men to rise in Roman society is evidence of early Gallo-Roman acculturation.

Caesar first mentions Valerius Troucillus in Bellum Gallicum 1.19, when the Roman commander is made aware of questionable loyalties among the Celtic Aedui, Rome's allies in central Gaul since at least the 120s BC. Caesar represents this divided allegiance in the persons of two brothers, the druid Diviciacus, who had appeared before the Roman senate a few years earlier to request aid against Germanic invaders, and the enterprising populist Dumnorix, who was the leading Aeduan in terms of wealth and military power. Dumnorix stood accused of conspiring with the enemy Helvetii; when Caesar holds a confidential discussion with his friend Diviciacus, he dismisses the usual interpreters and calls in Troucillus. Caesar describes Troucillus as a leading citizen of the province of Gallia Narbonensis and his personal friend (familiaris), adding that he placed the highest trust (fides) in the Helvian in all matters.

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