Q From Ron Witton, Australia: Why does sending someone away with a flea in their ear mean they have been given a rebuke?
A This expression goes back a long way. It appeared in English for the first time about 1430 in a devotional work with the title (in modernised spelling) The Pilgrimage of the Life of the Manhood, in which the last word meant the state or condition of being human. It was a translation of a work in French of about a century earlier by the Cistercian monk Guillaume de Deguileville.
Intriguingly, the French expression then had a different sense, of provoking or having amorous desire, though de Deguileville used it figuratively for a spiritual emotion that was evoked by the contemplation of great wonders. The amorous sense was still in the French language when Jean de la Fontaine wrote in the seventeenth century:
A longing girl
With thoughts of sweetheart in her head,
In bed all night will sleepless twirl.
A flea is in her ear, ’tis said.
In modern French, to have a flea put in your ear is that somebody is putting a suspicion into your head. The same expression occurs, with much the same sense, in other European languages, including German, Italian and Greek. In Dutch, it’s a way to say that you’re fidgety or restless. In English it principally refers — as you say — to a stinging reproof, though to send a person away with a flea in their ear can mean to snub them or angrily refuse a request.
The root association must surely be the result of getting a literal flea in one’s ear, something that wasn’t so rare in earlier times when hygiene was poor and houses — and their occupants — were often infested with fleas. A flea entering one’s ear would jump about in its attempts to get out and bite in frustration. It’s hard to imagine anything more vexatious or frustrating — it’s known to have driven some people almost mad (the old remedy was to pour oil into the ear, which drowned the flea).
It’s curious how so many different implications have been drawn from one simple circumstance. A flea moves fast, so it may have suggested something desirable but unattainable, or a thing that’s excitable and uncontrollable like a sudden passion. A flea may have been thought to be an external influence that whispered messages of distrust or ardour into the ear. English speakers may have judged that the physical and emotional discomfort aroused by a flea in the ear resembled severe criticism or rebuke. It may be that several of these ideas fused in various language versions of the expression.