LATIN DICTIONARYLexicon Latīnum
suffix

-per

-per

Meaning

  1. morphemeSuffix used in the formation of adverbs from either adjectives or other adverbs, having the (often, but not strictly temporal) sense of "thoroughly" or "throughout"
    semel (“once, a single time”) → semper (“always, ever ("once throughout")”)

Origins

  1. Proto-Indo-European*per-
  2. Proto-Italic*per
  3. Latin-per

Latin -per From per (“through”). Cognate of Ancient Greek περ (per), an intensifying postparticle.

Quick answers

What does -per mean in Latin?
-per, a suffix, means “Suffix used in the formation of adverbs from either adjectives or other adverbs, having the (often, but not strictly temporal) sense of "thoroughly" or "throughout"”.
Where does -per come from?
Proto-Indo-European *per- → Proto-Italic *per → Latin -per.