Alexander Schmidt, Shakespeare Lexicon and Quotation Dictionary

Protest, vb. 1) to declare with solemnity, to asseverate; absol.: “after we had embraced, kissed and --ed,” Wiv. III, 5, 75 (i. e. declared our love). “none is left to p.” Ado IV, 1, 289. With against (== to contradict solemnly): “but then you'll think -- which I p. against -- I am assisted by wicked powers,” Wint. V, 3, 90. With an accus. denoting the thing averred: “do me right, or I'll p. your cowardice,” Ado V, 1, 149. “that, on mine honour, here I do p.” Tit. I, 477. “the lady --s too much,” Hml. III, 2, 240. “said nothing but what I p. intendment of doing,” Oth. IV, 2, 205. Double accus.: “p. me the baby of a girl,” Mcb. III, 4, 105 (== to be the b.). Accus. denoting the effect: “--ing oath on oath,” Shr. II, 311. The person with to: “I p. to you,” Wiv. II, 2, 201. IV, 2, 33. Rom. II, 4, 183. Per. IV, 6, 95. Dat. and accus.: “when I p. true loyalty to her,” Gent. IV, 2, 7. With an inf.: “whom I p. to love,” All's IV, 2, 28. Oftenest with a subordinate clause: the which (her heart) “by Cupid's bow she doth p. he carries thence,” Ven. 581. “I do p. that I have wept,” Gent. IV, 4, 149. Wiv. II, 1, 75. Wiv. II, 1, 75 Meas. V, 344. Err. III, 1, 112. V, 2. Ado IV, 1, 282. Ado IV, 1, 282 LLL I, 1, 176. II, 158. V, 2, 352. V, 2, 352 V, 2, 352 Merch. IV, 1, 290. As IV, 1, 110. IV, 3, 21. All's II, 3, 73. IV, 3, 246. Tw. I, 5, 94. III, 4, 330. V, 173. John II, 501. R2 II, 3, 11. V, 6, 45. H4A V, 1, 25. H6A IV, 2, 19. H6C III, 3, 181. R3 I, 1, 52. II, 1, 26. III, 2, 81. Troil. II, 2, 138. Rom. III, 1, 71. Tim. III, 2, 86. Caes. III, 1, 238. Lr. V, 3, 130. Oth. II, 3, 333. III, 1, 50. IV, 2, 211. Per. II, 5, 27.
2) to promise solemnly, to vow: “on Diana's altars, to p. for aye austerity and single life,” Mids. I, 1, 89. “do villany, do, since you p. to do't, like workmen,” Tim. IV, 3, 437. cf. LLL V, 2, 410. Peculiar passage: “many unrough youths that even now p. their first of manhood,” Mcb. V, 2, 11 (vow to try. According to Johnson, it means here to prove, to give evidence of).
Not understood by the nurse in Rom. II, 4, 189.