EPI- n.
A prefix, meaning upon, beside, among, on the outside, above, over. It becomes ep- before a vowel, as in epoch, and eph- before a Greek aspirate, as in ephemeral.
EX- n.
s, it intensifies the meaning; in others, it has little affect on the signification. It becomes ef- before f, as in effuse. The form e- occurs instead of ex- before b, d, g, l, m, n, r, and v, as in ebullient, emanate, enormous, etc. In words from the French it often appears as es-, sometimes as s- or é-; as, escape, s…
EXHAUST v.
To drain, metaphorically; to use or expend wholly, or till the supply comes to an end; to deprive wholly of strength; to use up; to weary or tire out; to wear out; as, to exhaust one's strength, patience, or resources. A decrepit, exhausted old man at fifty-five. Motley.