unseldom

un- +‎ seldom

unseldom (comparative more unseldom, superlative most unseldom)

1. (archaic) Not seldom; frequently.
   • 1813 January 27, [Jane Austen], chapter 5, in Pride and Prejudice, volume II, London: […] [George Sidney] for T[homas] Egerton […], OCLC 38659585:

     When Mr. Collins said any thing of which his wife might reasonably be ashamed, which certainly was not unseldom, she involuntarily turned her eye on Charlotte.

   • 1878, William Morris, “The Decorative Arts: Their Relation to Modern Life and Progress.” An address delivered before the Trades’ Guild of Learning. London: Ellis & White, p. 21,

     For as was the land, such was the art of it while folk yet troubled themselves about such things; it strove little to impress people either by pomp or ingenuity: not unseldom it fell into commonplace, rarely it rose into majesty; yet was it never oppressive, never a slave’s nightmare or an insolent boast: and at its best it had an inventiveness, an individuality, that grander styles have never overpassed […]

   • 1921, Walter Harris, Morocco That Was, Edinburgh: W. Blackwood & Sons, p. 17,

     Mulai Abdul Aziz was, at the time of his succession (1894), about twelve or thirteen years of age. He was a younger son of the late Sultan, for Islamic thrones do not necessarily descend by primogeniture. It is not unseldom a brother who succeeds, and at times even more distant relations.

Almost exclusively used in the pleonastic phrase "not unseldom", meaning not infrequently.

• Mouldens, mouldens