late 14c., dilaten, "describe at length, speak at length," from Old French dilater and directly from Late Latin dilatare "make wider, enlarge," from dis- "apart" (see dis-) + lātus "broad, wide, widespread, extended" (see latitude). Meaning "expand, distend, spread out, enlarge in all directions" (transitive) is from early 15c.; intransitive sense of "spread out, expand, distend" also is from early 15c. A doublet of delay. Related: Dilated; dilating.
"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).
1540s, "enlargement" in any dimension, from Latin amplificationem (nominative amplificatio) "a widening, extending," noun of action from past-participle stem of amplificare "to enlarge, broaden, increase," from amplus "large" (see ample) + combining form of facere "to make, do" (from PIE root *dhe- "to set, put"). Originally in English often of rhetorical devices; meaning "enlargement of sound by electrical technology" is from 1915.
c. 1400, dilatacioun, "act of expanding, expansion," especially "abnormal enlargement of an aperture of the body," from Old French dilatation and directly from Late Latin dilatationem (nominative dilatatio) "a widening," noun of state from past-participle stem of Latin dilatare "make wider, enlarge," from dis- "apart" (see dis-) + lātus "broad, wide, widespread, extended" (see latitude). Also in Middle English "amplification in discourse" (late 14c.). In gynecology dilatation and curettage is by 1896.