to drop suddenly off
Note by H Craik to chapter 6 of the Tale of a Tub

Observe the awkward ending with a preposition — a fault which is so frequent with Swift as to be his almost invariable habit, where there is an opportunity. Cf. 1. 4 on this page, and p. 136, 1. 16; p. 142, 1. 28; and p. 143, 1. 29. innumerable other instances might be cited.