Jana Šebetková Etymology, topic 1
According to the Online Etymology Dictionary, the verb to fret has roots in Old English. It comes from the verb fretan, which means to devour or to consume. In Proto-Germanic people had the verb fra-etan (to eat up), which concludes two parts – fra means completely and etan to eat. This verb has also connections to the Dutch word vreton, Old High German freggan, Gothic fraitan and German fressen. In Middle English this verb was used for animals’ eating, too. Modern German still distinguishes essen for humans and fressen for animals. However, there was one more meaning of this verb, which is “wear away by rubbing or scraping” in 1200s. This meaning probably came from sound association with the Anglo-French forms of Old Frend fronter, meaning to rub, to wipe, to beat. And this word should have its roots in Latin fricare (to rub). Since 1200 there was also figurative meaning of this verb and it started to express emotions. It got meaning to worry, to vex. Also intransitive sense (be worried, vex oneself) was used around 1550s.