+ before (that) time, + heretofore, of late (old), + times past, yester(day)

Concise Bible Dictionary:

The word yesterday is used for the previous day (Ex. 5:14; John 4:52; Acts 7:28); and for past time indefinitely, as “a thousand years in Thy sight are but as yesterday;” and as when the Lord Jesus is said to be “the same yesterday, today, and forever” (Psa. 90:4; Heb. 13:8). It is used also as if of “no duration,” as “we are but of yesterday” (Job 8:9). Yesternight is the same as would now be called “last night” (Gen. 19:34; Gen. 31:29,42).

Strong’s Dictionary of Hebrew Words:

Transliteration:
’ethmowl
Phonic:
eth-mole’
Meaning:
or tithmowl {ith-mole'}; or methmuwl {eth- mool'}; probably from 853 or 854 and 4136; heretofore; definitely yesterday
KJV Usage:
+ before (that) time, + heretofore, of late (old), + times past, yester(day)