Here, in the middle of the well-known simile that depicts Aeneas and Turnus as bulls fighting for territory and a herd (12.715–22), Vergil registers the reactions of the onlookers. Commentators and lexicographers disagree about what the heifers are doing, interpreting ‘mussant’ in different ways. Servius (followed by Conington–Nettleship) glosses the verb as ‘dubitant’. By contrast, Heyne offers the paraphrase ‘anxii expectant’, responding to the theme of fear in the two preceding cola: cf. ‘pavidi’ and ‘metu’. Forbiger's explanatory ‘tacite expectant’ stresses rather the note of silence introduced by ‘stat pecus omne metu mutum’. Lewis and Short (s.v., II) and Georges (s.v., 112) concur with Forbiger when they translate ‘mussant’ ‘expect in silence’ and ‘stumm harren’. Other authorities, however, underscore the verb's onomatopoeic sense. Julius Caesar Scaliger, for example, observes of Vergil's usage: ‘sane verbum factitium, neque absonum a bourn voce’. Accordingly, some older commentators interpret ‘mussant’ as a restrained form of ‘mugiunt’. More recently, the OLD (s.v., 3a) and TLL (s.v., II2b [8.2.1709.26–32]) cite Aen. 12.718 under the definitions ‘mutter in indecision’ and ‘mussantem (i.e. murmurantem) dubitare’. Although there is general agreement that ‘mussant’ (followed by indirect deliberative questions) connotes uncertainty, there still remains the problem of whether it indicates silence, faint lowing, or muttering. The purpose of this note is to call attention to an unrecognized etymological wordplay in line 718 (‘stat pecus omne metu mutum, mussantque iuvencae’) which helps explain what the heifers are doing and why there are varying interpretations of ‘mussant’.