ERST

PRONUNCIATION: (uhrst)

MEANING: adverb: Formerly: in the past.

ETYMOLOGY: From Old English ǣrest (first), superlative of ǣr (early). Ultimately from the Indo-European root ayer- (day, morning), which also gave us early and ere. Earliest documented use: before 1150. The word is more commonly found in the adjective form erstwhile.
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ERAST - rubbed out

ERSAT - one fake (several would be "ersatz")

'EREST - what G-d do on the seventh day