Definition of "unseldom"

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.

1813 January 27, [Jane Austen], chapter V, in Pride and Prejudice: […], volume II, London: […] [George Sidney] for T[homas] Egerton, […], page 52

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: […]

, William Morris, The Decorative Arts: Their Relation to Modern Life and Progress […], London: Ellis and White, […], page 21

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.

1921, Walter B[urton] Harris, “The Moorish Court. I. The Accession of Mulai Abdul Aziz.”, in Morocco That Was, Edinburgh, London: Wiliam Blackwood and Sons, page 17