im·me·mo·ri·al 
(ĭm′ə-môrē-əl)
(ĭm′ə-môrē-əl)adj.
Reaching beyond the limits of memory, tradition, or recorded history.
[Medieval Latin immemoriālis : Latin in-, not; see IN-1 + Latin memoriālis, memorial; see MEMORIAL.]
im′me·mori·al·ly adv.