What is the X in X-mas?
c.1600, from Late Latin impraegnatus "pregnant," past participle of impraegnare "to render pregnant," from assimilated form of in- "into, in" (see in- (2)) + praegnare "make pregnant" (see pregnant). Earlier in same sense was impregn (1530s).
impregnate im·preg·nate (ĭm-prěg'nāt)v. im·preg·nat·ed, im·preg·nat·ing, im·preg·nates
To make pregnant; to cause to conceive; inseminate.
To fertilize an ovum.
To fill throughout; saturate.