Green’s Dictionary of Slang

(Irish) a woman with thick ankles; thus beef to the heels/knees, like a Mullingar heifer; occas. used of men, to describe them as brawny, stalwart.

1811		Lex. Balatronicum n.p.: An Irish woman. A woman with thick legs is said to be like a Munster heifer; i.e. beef to the heels.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue [as cit. 1811].
1847		R.F. Walond Paddiana II 95: Faith, she’s a true Mullingar heifer – beef to the heels.
1848		Bell’s Life in Sydney 23 Dec. 3/1: [She] stands 3 feet 10, is nearly a cube of solid fat, legs, ankles of the true Mullingar breed, .
1851		London Standard 2 Sept. 3/5: The first idea [...] on entering Mullingar is to look out for a realisation of the lines ‘Beef to the heels, like a Mullingar heifer,’ which are unjustly applied to its fair inhabitants.
1864, 1867, 1870		Hotten Sl. Dict.
1873		N.S. Dodge ‘Vagrants and Vagrancy’ in Appleton’s Journal (N.Y.) 6 Sept. 308: The origin of the vagrant words for fine girl, Mullingar heifer, is too good to be left untold: Many years ago a traveler, passing through Mullingar, was struck with the thick ankles of the women, and made inquiry about the local peculiarity. ‘May I ask,’ said he to a strapping girl, ‘if you wear hay in your shoes?’ ‘Faith an’ I do,’ replied the damsel, ‘and what then?’ ‘Oh, nothing,’ added the stranger, ‘only that accounts for the calves of your legs coming down to fodder.’.
1876		Derby Mercury 11 Oct. 6/2: The domestic economy of the household was occupied by a middle-aged woman, with ankles like those of the Mullingar heifer.
1883		Taunton Courier 17 Jan. 5/2: The dancing itself was of rare merit and grace, and [...] there was not a ‘Mullingar heifer, beef to the heels,’ amongst the whole bevy of beauty.
1908		L. Doyle Ballygullion (1927) 33: She had her skirts well kilted up for the runnin’, an’ she made no great sight, I can tell ye; for she was beef to the heels like a Mullingar heifer.
1936		M. Harrison All the Trees were Green 230: The older ladies will exhibit ankles like a Mullingar heifer’s as they paddle.
[1971		Current Sl. VI 6: Heifer legs, n. A girl with large calves].
1979		K. Bonfiglioli After You with the Pistol (1991) 252: She was a massive creature, all beef down to the ankles, just like a Mullingar heifer.
1982		N. Keesing Lily on the Dustbin 13: One correspondent wrote of a person having ‘legs like a Mullingar heifer’. Weeks later a woman told me, ‘One thing my father often said was “She has a face like a Mullingar heifer”.’.
2014		T. Black Artefacts of the Dead [ebook] Here was an Ayrshire heifer — all beef to the heels — stampeding into his midst. [...] She stomped through the mass of bodies with all the grace of a bulldozer.