ETYMOLOGY
from im- + memorious
EXAMPLE
“…And we like wretches, carelesly oreseene
Neglecting all continuance of our good,
Of our owne birth haue immemorius beene,
And quite forgot the Nephewes of our blood,
And of neere kin are growne meere strāgers rather,
Almost forgetting we had all one father…”
From: Svvord and Buckler, or, Seruing-Mans Defence
By William Basse, 1602
Lexicophilia 