Green’s Dictionary of Slang

1. a short cropped beard.

1859		Hotten Dict. of Modern Sl. etc. xlix: The ‘fast’ men of buried Nineveh, with their knotty and door-matty looking beards, may have cracked Slang jokes on the steps of Sennacherib’s palace.
1892		in Punch 8 Oct. 165: My general name among chance acquaintances is ‘Old Doormat.’ You can judge how thick my hair must be.
1909		(ref. to 1850s–80s) J. Ware Passing Eng. of the Victorian Era 115/2: Door-mat (Colloquial, 1856). The name given by the people to the heavy and unaccustomed beards which the Crimean heroes brought home from Russia in 1855–56, and which started the beard movement [...] By 1882 the term came to be applied to the moustache only, probably because about this time the tendency to shave the beard and wear only a very heavy moustache became prevalent.
1912		Bulletin (Sydney) 17 Oct. 5/2: The blithest stroller on the Block / Will have great doormats on his chin.
1930		Hull Dly Mail 25 June 11/1: The Juge d’Instruction ran his fingers through his doormat of a beard.

2. (Aus.) a woman's short hairstyle.

1880

Bulletin (Sydney) 23 Apr. 8/4: The girl with the ‘door-mat’ hair and cardinal ‘oh-we-never-mention-’ems’.

3. a moustache.

1909

see sense 1.