Commentary for Nazir 55:5

And it is taught - [this term] is being used as a support for [the previous statement].

One who enters etc. in a wagon, boat or raft -- that is to say, in a large boat which is equipped with an iskareya -- and is it called this [iskareya] because of its iskareya, which is a mast. And it is called POST or MAST in a foreign language. Because it is a frequently-occurring case, the Sages decreed regarding it. This baraita is according to Rabbi Yosei, son of Rabbi Yehuda.