"to enlarge a hole," especially "to widen or enlarge by the use of a rotary cutter," 1815, a word of "somewhat doubtful origin" [OED], but it is probably a southwest England dialectal survival from obsolete Middle English reme "to make room, open up, extend by stretching."
This is from Old English ryman "widen, extend, enlarge," from Proto-Germanic *rumijan (source also of Old Saxon rumian, Old Norse ryma, Old Frisian rema, Old High German rumen, German räumen"to make room, widen"), from *rumaz "spacious" (see room (n.)). Related: Reamed; reaming; reamer.
Especially with out (adv.). The slang meaning "to cheat, swindle" is recorded by 1914; the sexual sense is attested by 1942. To ream (someone) out in the sense of "to scold, reprimand" is recorded from 1950; earlier it was used of gun barrels, machinery, etc., "to remove (a jam or defect) by reaming" (1861).
late 14c., relaxen, "to make (something) less compact or dense" (transitive), originally especially in medicine, of muscles, etc., from Old French relaschier "set free; soften; reduce" (14c.) and directly from Latin relaxare "relax, loosen, open, stretch out, widen again; make loose," from re- "back" (see re-) + laxare "loosen," from laxus "loose" (from PIE root *sleg- "be slack, be languid"). A doublet of release.
Meaning "decrease tension" is from early 15c. From 1660s as "to make less severe or rigorous." Intransitive sense of "become loose or languid" is by 1762; that of "become less tense" is recorded from 1935. Of persons, "to become less formal," by 1837. Related: Relaxed; relaxing. As a noun, "relaxation, an act of relaxing," from 17c.