I can see it now. A bunch of burlesque dancers dropping that particular peice of clothing on the floor and one of them saying " oh my, they look just like Times Roman small case “g"s with their loops connected. We will have to call these small case TR g-strings.” The rest of the group agreed with the original outspoken, creative member of the group. Common usage seems to have dropped their more descriptive, but long and formal, term for this very creative bit of clothing.
From the column:
I think he almost gets it at this point but the most probable source is a “girding” string as when one “girds their loins”.
From http://dictionary.reference.com/search?q=gird
gird (gûrd)
v. gird·ed, or girt (gûrt) gird·ing, girds
v. tr.
**To encircle with a belt or band.
To fasten or secure (clothing, for example) with a belt or band. **
To surround. See Synonyms at surround.
To equip or endow.
To prepare (oneself) for action.
gird
\Gird, v. t. [imp. & p. p. Girtor Girded; p. pr. & vb. n. Girding.] [OE. girden, gurden, AS. gyrdan; akin to OS. gurdian, D. gorden, OHG. gurten, G. g["u]rten, Icel. gyr?a, Sw. gjorda, Dan. giorde, Goth. biga['i]rdan to begird, and prob. to E. yard an inclosure. Cf. Girth, n. & v., Girt, v. t.] 1. To encircle or bind with any flexible band.
**2. To make fast, as clothing, by binding with a cord, girdle, bandage, etc.
- To surround; to encircle, or encompass.**
That Nyseian isle, Girt with the River Triton. --Milton.
- To clothe; to swathe; to invest.
I girded thee about with fine linen. --Ezek. xvi. 10.
The Son . . . appeared Girt with omnipotence. --Milton.
- To prepare; to make ready; to equip; as, to gird one’s self for a contest.
Thou hast girded me with strength. --Ps. xviii. 39.
To gird on, to put on; to fasten around or to one securely, like a girdle; as, to gird on armor or a sword.
Let not him that girdeth on his harness boast himself as he that putteth it off. --1 Kings xx. 11.
To gird up, to bind tightly with a girdle; to support and strengthen, as with a girdle.
He girded up his loins, and ran before Ahab. --1 Kings xviii. 46.
Gird up the loins of your mind. --1 Pet. i. 13.
I am flabbergasted to discover that no real progress has been made on this question since Cecil’s 1980 column. The links above are dead so here’s the column on the Wayback Machine.
The best recent discussion I could find is a 2017 answer on StackExchange that includes a few hits from the early 20th century, although they don’t explain anything.
Get going gurus, and give us the genuine gospel that guarantees good if not great gratification. And no more gossip.
I have nothing to contribute except to thank Exapno. ¡Gracias! 
For once, a decades-old thread WORTH reviving!
And, maybe someone could email the good folks at “Word Matters,” the delightful and informative podcast run by three folks at Mirriam-Webster. This is right up their alley.
Did you know that a properly made G-string requires 27 feet of string? Surprising but true.