Definition of "wantwit"

[…] and ſuch a Want-wit ſadnesse makes of mee,That I haue much ado to know my ſelfe.

c. 1596–1598 (date written), William Shakespeare, “The Merchant of Venice”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene i], page 163, column 1

'Wantwit! Clod-brain! Numbskull!' he shouted, straddling her midriff and pummelling her face and chest with his fists.

2017, Minette Walters, The Last Hours, page 357