These names are in Gaelic Maolagan, Olr. Maelecan, a double diminutive of moel (-oc-an), 'the little bald or shaven one,' probably in allusion to the ancient Gaelic tonsure. The first form is common in Galloway. Macrath ap Molegan of Wyggetone, who rendered homage in 1296 (Bain, II, p. 198) is apparently the first of the name recorded in Scotland. As Makerathe Molgan he had his lands restored to him in the same year (ibid., p. 218). Cymric 'ap,' afterwards reduced to A is possibly due to Cymric influence. Thomas Ameligane, a witness in Dumfries, 1477 ( Edgar, p. 227), may be Thomas Arnul-igane, chaplain and notary public at Wigtown, 1485 (RMS., II, 1024). The name also appears in Perth in 1408 as Milikyn (Milne, p. 58). George Aruligane was burgess of Dumfries, 1510 (RMS., II, 3513), and a Schir William Amuligan, a cleric, is mentioned in the same year (Bucc. MS S., p. 14). Thomas Amuligane, a follower of the earl of Cassilis, had a respite for murder committed by him in 1526 (RSS., I, 3386), Cuthbert Amullekyne of Dempstartoune was "dilaitit of the cryme of adulterie" in 1578 (Trials, I, p. 78), and John Amiligane witnessed a sasine in Dumfries, 1595 (RRM., III, p. 394). John Myllikin, a 'vabster aid and puir,' was buried in Dysart, Fife, at public expense, 1593 (Dysart, p. 41), another Johnne Arnulliekin was hanged in 1612 (Trials, III, p. 223), and John Mulligane, polentarius (i.e. maltster), burgess of Dumfries, was retoured heir in lands in regality of Lyncluden, 1630 (Retours, Kirkcudbright, 183). James Myllighame of Blakmyre was retoured heir of his father in lands in parish of Balmaclellane and Dairy, 1633 (ibid., 200). Robert Mulligane, 'ludimagister' (i.e. master of the play), burgess of Edinburgh, 1649 (Inquis., 3556) is most probably Robert Mulligin designated vulgar (i.e. public) schoolmaster who was married in 1656 (Edinb. Marr.). Thomas Mulliken in Cargat was charged with hamesucken in 1672 (Just. Rec., II, p. 84). Major James Milliken purchased part of the ancient barony of Johnstone, Renfrewshire, in 1733, and gave the estate the name of Milliken (Stodart, II, p. 260). Robert Andrews Milliken, the American scientist, is of Scottish descent. Millagain 1684, Milligain 1694, Mulikyn 1480, Mulligine 1668, Mullikine 1662. There is a name (Mulekyn) in the Exchequer Rolls which might be thought a variant of this. The bearers of II, however, were Italians. In 1364 there is an entry of payment to Donatus Mulekyn for ornaments for the king (ER., II, p. 160), and in the thirty-second year of David 11 (1361-62) James or Jacobus Mulekyn "of Florence," probably a relative, was master moneyer (monetarius) in Edinburgh (ibid., II p. xciii).

(Celtic) for the Irish 0'Maoil(e)a- cáin, O’Maoil(e)agáin, Grandson or Descendant of Maolacán, Maolagán = the Little Bald or Shaven One, Monk, Disciple [Irish maol, bald, &c. + the double diminutive suff. -ac-án, (for -óc-án,) -ag-án (for -óg-án]

O'Milligan, an ancient Irish name.