Where does "to stick out like a sore thumb" come from?

A sore thumb which had been (heavily) bandaged would be very noticeable in its white covering, and would also be largely immoveable, and would 'stick out' at an unusual angle.

to be easily noticed as different.

http://idioms.thefreedictionary.com/stick+out+like+a+sore+thumb

If something sticks or stands out like a sore thumb, it is clearly and obviously different from the things that are around it.

http://www.usingenglish.com/reference/idioms/stick+out+like+a+sore+thumb.html

not fit or blend, look out of place

http://bits.westhost.com/idioms/id571.htm

1. Said of a wound, injury, part of the body, etc: painful or tender.

Thesaurus: sensitive, irritated, painful, tender, raw, aching, inflamed, smarting.

2. Said of a blow, bite, sting, etc: painful or causing physical pain.
3. Causing mental anguish, grief or annoyance.

Example: a sore point

(N Amer, especially US)
4. Angry or resentful.

Example: got sore at the kids

5. Severe or urgent.

Example: in sore need of attention

http://www.allwords.com/word-stick%20out%20like%20a%20sore%20thumb.html

The OED, which defines the phrase as meaning being conspicuous or obvious, quotes for its two earliest examples Erle Stanley Gardner, author of numerous books about Perry Mason, whose exploits as detective need no introduction for most people.

"1936 E. S. GARDNER Case of Sleepwalker's Niece xiii. 128 'No,' he said, 'that's the one thing in the case that stands out like a sore thumb, now that I stop to think of it.' 1941 {emem} Case of Haunted Husband (1942) xvi. 126 A private detective in that atmosphere would stick out like a sore thumb on a waiter serving soup."

A sore thumb which had been (heavily) bandaged would be very noticeable in its white covering, and would also be largely immoveable, and would 'stick out' at an unusual angle.

http://www.phrases.org.uk/bulletin_board/35/messages/261.html

There are several different possibilities:

A sore thumb is swollen and sticks out due to its large size.

A sore thumb is likely to be red and stick out because of its color.

A sore thumb is more likely to be held away from the hand at an odd angle, making it "stick out."

A sore thumb could be bandaged, making it white, larger, and more distinctive.

If anyone knows of the specific origins I would love to know what the "real" reason is, since everything seems to be speculation.