corrugate (v.)

word-forming element usually meaning "with, together," from Latin com, archaic form of classical Latin cum "together, together with, in combination," from PIE *kom- "beside, near, by, with" (compare Old English ge-, German ge-). The prefix in Latin sometimes was used as an intensive.

Before vowels and aspirates, it is reduced to co-; before -g-, it is assimilated to cog- or con-; before -l-, assimilated to col-; before -r-, assimilated to cor-; before -c-, -d-, -j-, -n-, -q-, -s-, -t-, and -v-, it is assimilated to con-, which was so frequent that it often was used as the normal form.

1775, in zoology, anatomy, etc., "a fold or wrinkle," plural of ruga (1775), from Latin ruga "a wrinkle in the face," from Proto-Italic *rouga-, which is of uncertain origin. "Since words for 'wrinkle' and 'crease' are often derived from 'to be rugged', from which also 'to belch' is often derived ..., the most obvious connection is with e-rugere 'to belch'" [de Vaan].  Related: Rugate; rugulose; rugose (1703); rugosity (1590s).