‘Hoots’ or ‘hoot’, in the words of the OED, seems to be a ‘natural utterance of objection or revulsion’. I am delighted by this natural utterance. The Concise Scots Dictionary describes it as ‘expressing dissent, incredulity, impatience, annoyance, remonstrance or dismissal of another person’s opinion’. In English you might say an equivalent is ‘tut’, or maybe ‘tush’. It’s recorded in the OED corpus as being recorded from the 1680s. There are similar sounds of disapproval in Swedish (hut begone, used in taking one up sharply), Welsh (hwt off! away!), Irish (ut out! pshaw!), Gaelic (ut! ut! interj. of disapprobation or dislike).
An additionally delightful thing is that the OED thinks that hoot as an interjection might have originally been an attempt to echo of the sound of hoolets! The vowel sound u is heard at the furthest distances, so hoot sounds, or ‘hoo’, or ‘ooohoo‘ are often used in calls. The Middle English hūten is found from c1200, for example. Cooooooool!