Sentence:  Hi-Cinsellah, when he deemed my arm could help to prop his crazy throne, swore to <WSD>handlock</WSD> me in marriage with his daughter Eva, but, seeing the tide swept too strong against us, he cast me off as a  broken oar, sens the princess and her maidens to the convent of St. Bridget in Cilldair, and with sixty followers, all his muster, scours away to England's king, to purchase with her hand his aid in the war he is about to wage with Eire. 
Meaning of the word marked with <WSD> tags:  To restrain with, or as with, a handlock.