Green’s Dictionary of Slang

1. a teasing name for a tall, thin person.

1849		Sam Sly 6 Jan. 3/1: He advises the walking lamp post of Shoe-lane, not to be so parpicular [sic] in his attention to M———y A———, as it looks particularly ridiculous.
1892		Illus. Police News 26 Nov. 4/1: ‘Strike me dumb, Sam,’ replied the tall lamp-post specimen of humanity.
1918		K.F. Purdon Dinny on the Doorstep 129: Well, g’lang ou’er that, ye dirty long streel of a lamp-post, yeh!
1937–84		Partridge DSUE (1984) 663: from ca. 1870.
1952		B. MacMahon Children of the Rainbow 88: Sweatin’ blood poor Mary must be, herself and the lamp-post of a man!
1959		I. & P. Opie Lore and Lang. of Schoolchildren (1977) 189: Thin people inspire almost as many names [...] lamp-post, walking lamp-post.

2. (Aus.) a long cigarette end.

1920

Advocate (Burnie, Tas.) 5 June 7/2: ‘Give us a wagonette’ [...] ’Only got coffin-nails.’ ‘Nothing doing. Sooner look for lamp-posts’.

3. (US) any large and noticeable piece of jewellery.

1922

Appleton Post-Crescent (WI) 8 May 11/1: Flapper Dictionary lamp post – Any noticeable piece of jewelry.