If you look up the word truie (the French word for ‘sow’) in the 1992 edition of the Dictionnaire historique de la langue française (published by Robert), you will find the following definition (which I have translated):

Feminine noun (13th century) from the Low Latin troia (8th century, Gloses de Cassel [a small Germano-Roman lexicon]), derived from porcus troianus (‘Trojan pig’), which in Low Latin means a pig stuffed with small game, a jocular allusion to the Trojan horse. The term must have been turned first into porcus de Troia, then simply troia by ellipsis. [The French etymologist] Pierre Guiraud believes the term is applied to a sow because it is ‘stuffed’ with piglets.

Now turn to volume 6 of the 2001 edition of Le Grand Robert de la langue française and its very slightly modified account of the etymology of truie: it indicates that the word may possibly (my italics) derive from porcus troianus. The reason for the uncertainty is twofold: in Classical Latin there is only one mention of porcus troianus as such. It is to be found in Martial (49), and would seem to be a simple conceit by that wittiest of poets rather than a common name given to a stuffed pig. But the term subsequently went ‘viral’ – to use modern computer-speak – in countless texts and commentaries mentioned and described by scholiasts and copyists down the centuries. The other reason for there to be some doubt about a direct ‘borrowing’ from troia to truie is that there is some strong evidence to suggest that the French word is in fact derived from a Gaulish etymon trogja, to judge from the distribution of the word truie in the Gallo-Roman area (northern Italy, Catalonia and Sicily).

Emile Littré, in his celebrated 19th-century French dictionary, echoes this view by citing a multitude of words for a sow, namely the Walloon trauie, the Burgundian treue, the Berrichon treue, the Occitan trueia and truiga and the Catalan truja. The Irish and Breton words for a pig, torc and tourc’h respectively, would seem to have resulted from a process of metathesis, or the transposition of two sounds or letters in a word (as in ‘bird’, which evolved from ‘brid’ in Middle English).

The lesson to be learnt from the way the 1992 edition of the Robert dictionary categorically asserts that truie derives from troianus is that people tend to believe in what they already believe. This is what is known as confirmation bias, which encourages overconfidence in personal beliefs and can maintain or strengthen convictions in the face of contrary evidence. It lies at the heart of almost every folk – or false – etymology.

In the About section of my blog, I claimed (erroneously) that the French and Italian words for a ‘sow’, truie and troia respectively, were both derived from the ancient city of Troy. It had seemed an attractively neat explanation for their etymology. It turned out to be a case of confirmation bias. I have had to fall back on a much less evocative explanation. Put another way, I have had ‘to eat my words’ (more of which in a later post).