Wag

A "wag" is a guess at an answer, the result of a numerical hunch. Because of its similarity to the verb "wag" (an indistinct shaking) it stands as a shorthand for a hand-waving answer. The phrase is often rendered in verb form as "take a wag", e.g. We've got three different numbers, each equally invalid; we'll have to take a wag at it.

WAGs can be good or bad, depending on context. If you know the true measurement is between 10m and 20m and so you throw 15m into the equation, then you've made a WAG. If your equation doesn't require any more precision than that, then it's a good WAG. However, if you need to know the mass to within a millimeter, then don't take a WAG.

WAG

An arch-frolicsome fellow.

The 1811 Dictionary of the Vulgar Tongue.

Wag (?), v. t. [imp. & p. p. Wagged (?); p. pr. & vb. n. Wagging.] [OE. waggen; probably of Scand. origin; cf. Sw. vagga to rock a cradle, vagga cradle, Icel. vagga, Dan. vugge; akin to AS. wagian to move, wag, wegan to bear, carry, G. & D. bewegen to move, and E. weigh. 136. See Weigh.]

To move one way and the other with quick turns; to shake to and fro; to move vibratingly; to cause to vibrate, as a part of the body; as, to wag the head.

No discerner durst wag his tongue in censure. Shak.

Every one that passeth thereby shall be astonished, and wag his head. Jer. xviii. 16.

⇒ Wag expresses specifically the motion of the head and body used in buffoonery, mirth, derision, sport, and mockery.

© Webster 1913.

Wag, v. i.

1.

To move one way and the other; to be shaken to and fro; to vibrate.

The resty sieve wagged ne'er the more. Dryden.

2.

To be in action or motion; to move; to get along; to progress; to stir.

"Thus we may see," quoth he, "how the world wags." Shak.

3.

To go; to depart; to pack oft.

I will provoke him to 't, or let him wag. Shak.

© Webster 1913.

Wag, n. [From Wag, v.]

1.

The act of wagging; a shake; as, a wag of the head.

2. [Perhaps shortened from wag-halter a rogue.]

A man full of sport and humor; a ludicrous fellow; a humorist; a wit; a joker.

We wink at wags when they offend. Dryden.

A counselor never pleaded without a piece of pack thread in his hand, which he used to twist about a finger all the while he was speaking; the wags used to call it the thread of his discourse. Addison.

© Webster 1913.