The 'weaker vessel': blame Tyndale
How a cliche caught on:
"The phrase 'the weaker vessel' originated with Willian Tyndale's translation of the New Testament into English in 1526 and became common usage during the next hundred years or more. Many must have encountered it in the King James version of the Bible ... It is hard to think of a single phrase which brings together more aptly the whole Judaeo-Christian tradition of the subjection of women wiith the humoral physiology of the ancients."
Gender, Sex and Subordination in England 1500-1800, Anthony Fletcher, Yale University Press, New Haven and London, 1995, p. 60
As a book it has useful anecdotes, but is otherwise nothing to get excited about.