irregularity (n.)

early 14c., "violation of Church rules governing admission to clerical office," from Old French irregularité (14c.) and directly from Medieval Latin irregularitas "irregularity," from irregularis "not regular" (see irregular (adj.)). Meaning "that which is irregular" is from late 15c.; sense of "state of non-conformity to rule" is from 1590s; meaning "want of symmetry" is from 1640s.