infrequency (n.)

1670s, fact of being infrequent," from Latin infrequentia "a small number, thinness, scantiness," abstract noun from infrequentem (nominative infrequens) "occurring seldom, unusual; not crowded, absent," from in- "not" (see in- (1)) + frequens (see frequent). Older in this sense is infrequence (1640s). Earlier infrequency was used in a now-obsolete sense of "state of being unfrequented" (c. 1600).