IMMEMORIALLY
Etymology
Adverb
immemorially (comparative more immemorially, superlative most immemorially)
In an immemorial manner, from time immemorial.
Source: Wiktionary
Im`me*mo"ri*al*ly, adv.
Definition: Beyond memory. Bentley.
IMMEMORIAL
Im`me*mo"ri*al, a. Etym: [Pref. im- not + memorial: cf. F.
immémorial.]
Definition: Extending beyond the reach of memory, record, or tradition;
indefinitely ancient; as, existing from time immemorial. "Immemorial
elms." Tennyson. "Immemorial usage or custom." Sir M. Hale. Time
immemorial (Eng. Law.), a time antedating (legal) history, and beyond
"legal memory" so called; formerly an indefinite time, but in 1276
this time was fixed by statute as the begining of the reign of
Richard I. (1189). Proof of unbroken possession or use of any right
since that date made it unnecessary to establish the original grant.
In 1832 the plan of dating legal memory from a fixed time was
abandoned and the principle substituted that rights which had been
enjoyed for full twenty years (or as against the crown thirty years)
should not be liable to impeachment merely by proving that they had
not been enjoyed before.
Source: Webster’s Unabridged Dictionary 1913 Edition