What is "usipetes"

Usipetes or Usipii (in Plutarch's Greek, Ousipai, and possibly the same as the Ouispoi of Claudius Ptolemy) were an ancient tribe who moved into the area on the right bank (the northern or eastern bank) of the lower Rhine in the 1st century BC, putting them in contact with Gaul and the Roman empire. They are known first from the surviving works of ancient authors such as Julius Caesar and Tacitus. They appear to have moved position several times before disappearing from the historical record.

While the Usipetes were referred to by the Romans as Germanic rather than Gauls, their recorded names are most reasonably explained as Celtic: Usipetes translates as "good riders", and Caesar and others report them to have strong cavalry.