Learn English – Etymology of “duck”

I asked you which IE languages you know - in order to critically evaluate these three hypotheses, a strong background in the history of Latin (at least) is necessary. There are three major textbooks on the history of Latin - Baldi 1999, Sihler 1995, and Weiss 2009.

The first hypothesis is best supported by evidence - and, in fact, pretty standard now (for example, de Vaan 2008).

The Anlaut (word-initial) PIE *gwh> Lat. f sound correspondence is well documented, cf. Latin formus 'warm' - MnE warm; Greek thermos; Rus. zhar 'heat', goret' 'burn' etc. We still don't really know how PIE *gwh turned into Latin f (via *χw?) but this correspondence is regular.

We may ignore the perfectum fefelli because it's a relatively new coinage (double ll), cf. pello-pepuli, fero-tetuli (Meiser 1998), although reduplicated perfectum is usually archaic/rare in Latin.

The second "hypothesis" does not stand to scrutiny - supposedly, Latin fallo is derived from Latin facio. The person who came up with that hypothesis doesn't know Latin morphology at all. I don't know of any rule of Latin word-formation that could explain such a connection.

The third hypothesis does not have any explanation - it stops at Latin fallo.

"Apt" and "fit" are generally not interchangeable, as one or the other tends to be preferred in a given context. I think the degree of specificity is what distinguishes them. "Fit" tends to means "well-suited to a particular purpose", while "apt" means "well-chosen" or "appropriate" in a more holistic sense. Here are some examples:

• "This was an apt observation, given the events that followed." The observation was especially well chosen in context, not for any particular purpose, so "fit" doesn't really work here. However, "fitting" could be used.

• "The survey was designed to determine which candidate was most fit for the job." Since a specific purpose is cited, "fit" works better than "apt" here.

• "Joe proved an apt pupil, quickly surpassing his peers." Here, "apt" is used to mean "skillful" in a general sense, without any particular purpose.

• "Only the most physically and mentally fit students can become underwater basket weavers." Here the two words are pretty interchangeable, although perhaps "adept" would be better than "apt".