attenuate (v.)

"to make thin, to make less," 1520s, from Latin attenuatus, past participle of attenuare "to make thin, lessen, diminish," from assimilated form of ad "to" (see ad-) + tenuare "make thin," from tenuis "thin," from PIE root *ten- "to stretch." Related: Attenuated; attenuating. Earlier was Middle English attenuen "to make thin (in consistency)," early 15c.