filament

English "filament" was borrowed from Medieval Latin fīlāmentum, which grew from Late Latin fīlō ("to spin, draw out in a long line"), itself rooted in Latin fīlum, meaning "thread."

The word traveled from a verb meaning to spin thread out in a line, to a Medieval Latin noun for the thing spun, arriving in English as "filament" — any thin, thread-like strand.

The Latin suffix -mentum, seen here in fīlāmentum, is the same ending found in many English words borrowed through Latin, marking the result of an action — in this case, the result of spinning.