a. or adv. colloq. and dial. Also unbeknowns, etc. [f. prec. The analogy on which the -s or -st has been added is not clear: cf. the earlier UNKNOWNST.] = UNBEKNOWN 2.
1854. Huxley, in L. Huxley, Life & Lett. (1910), I. 111. I hate doing anything of the kind ‘unbeknownst’ to people.
1854. Poultry Chron., I. 331/1. It was found that she was sitting on a nest of eggs,—unbeknownst.
1887. Kipling, Plain Tales fr. Hills (1888), 147. Perhaps they were afraid that their wives had come from Homo unbeknownst.
