The word is a Latinism not apparently otherwise attested in French. It is a direct translation, it seems, of the Vegetius (AND: veg¹) Latin from the Nottingham manuscript, effetus, 'worn out, exhausted' (DMLBS); 'exhausted, worn out by bearing [young]' (Lewis and Short). Vegetius is the source of a significant number of Classical Latin borrowings (especially of technical military lexis) in Anglo-Norman. Effet (or effetus) is absent from the Base de civilisation romaine (XII^e-XV^e s.) hosted by ATILF (http://www.cnrtl.fr/lexiques/civirom/), and which contains in its corpus three versions of Vegetius: Jean de Meun’s, Jean Priorat’s abridgement of that text, and an Anglo-Norman text from Cambridge, Fitzwilliam Museum (DEAF: VégèceRichT; AND’s veg). Jean de Vignay’s translation of Vegetius (ed. Leena Löfstedt, Li livres Flave Vegece de la Chose de Chevalerie, Helsinki 1982, I.28 [p. 54]) handles this phrase rather differently: 'ne les terres qui engendrerent les Lacedomiens [...] et les forz Romains n’en sont mie portees'. That the word is apparently absent in the rest of the Vegetius tradition points towards its being a Latinizing hapax of the Nottingham translator. [Correct identification of this word: thanks to Michael Beddow.]