partly diving partly dictionary question

[Diver0001]

Can somebody tell me why in English horizontal diver's position is called "trim". I searched all dictionaries I have for the meaning of this word and the closest one I found is about the trim of the boat. Can somebody provide me a clear definition of the word "trim" in the diving sense as well as - and this is the dictionary part - where does this word come from?
So why trim is called trim????
Mania

I think it comes from flight. Neutral trim in an airplane is when it can maintain horizontal flight with the control surfaces level (probably a gross oversimplification if you're a pilot but ok....). The same term "neurtral trim" is used in submarines meaning more or less the same thing. If you dig a little you'll probably find this term used in a variety of similar ways like, for example, in scuba diving.

R..

 

[WJL]

The term "trim" as used in diving is an import from aviation, as used to describe an airplane's attitude in flight. These definitions are from Web WordNet 2.0:

4. trim -- (balance in flight by regulating the control surfaces; "trim an airplane")
5. trim -- (be in equilibrium during a flight; "The airplane trimmed")

How the word "trim" came to have this meaning for aircraft I can only guess. I surmise it was a spin off from the nautical use of the term meaning to balance the cargo to adjust the way a vessel rides in the water.

World Wide Words, http://www.worldwidewords.org/, one of my favorite web sites, explores the etymology of old and new English words. Michael Quinion, the author of the site, may find your inquiry regarding "trim" interesting enough to research the word if you contact him.

 

[Schwim]

More etymology from etymology online:

trim (n.)
"state of being prepared," 1590, nautical jargon, from trim (v.). The meaning "visible woodwork of a house" is recorded from 1884; sense of "ornamental additions to an automobile" is from 1922. Slang meaning "a woman regarded as a sex object" is attested from 1955, Amer.Eng.
trim (v.)
probably from O.E. trymman "strengthen, make ready," from trum "strong, stable," from P.Gmc. *trumaz; said to be cognate with Skt. drumah "tree," Gk. drymos "copse, thicket," drys "tree, oak," and O.E. treow (see tree). Examples in M.E. are wanting. Original sense is preserved in nautical phrase in fighting trim (see trim (n.)). Meaning "make neat by cutting" is first recorded 1530; that of "decorate, adorn" is from 1547. Sense of "reduce" is attested from 1966. The adj. sense of "in good condition, neat, fit" is attested from 1503, probably ult. from O.E. adj. trum.