I think the Oxford boys made a boo-boo here. Even the text they refer to (Horapollo 1.46) has εὐτονία ("vigor"), not ἐντονία. The word ἐντονία is attested nowhere else in either ancient or modern Greek. Leemans' 1835 edition of Horapollo shows all the MSS with εὐτονία; Leemans mentions that some previous editors had suggested ἐντονία. Modern editions of Horapollo have followed the MSS and Leemans in preserving εὐτονία. The passage in question is τὸ τηνικαῦτα τῇ ὑπερβαλλούσῃ εὐτονίᾳ τιτρώσκει τὴν θήλειαν ("which then wounds the female through overwhelming vigor"). I see no reason to read "through an overwhelming erection" by emending a unanimous text with a non-existent word ἐντονία.