Writing in 1682, the antiquarian Sir Henry Piers observed that the town's name, if rendered into English, imports the meaning "the short mill", a detail that quietly suggests milling was not incidental to the place but in some sense constitutive of it. That claim is easier to believe when you consider the River Brosna once supported several mills within the town's bounds, among them a structure known as Mullynnehouny, or Hamon's Mill, whose approximate site on the east bank of the river can still be traced, at least in outline, on later Ordnance Survey mapping.

The 1641 Survey of Mullingar described the mill's position with careful specificity: bounded to the north by the town bridge, to the east by Hamon's land, to the south by Prior Street (the old Austin Friars Street), and to the west by the town itself. The Hamon in question was William Hamon, recorded in 1641 as a merchant in Mullingar. By 1667, the mill had passed into a different legal context; a confirmation of a land grant to Sir Arthur Forbes under the Acts of Settlement and Explanation, the Restoration-era legislation by which land ownership in Ireland was renegotiated after the upheavals of the 1640s and 1650s, referred to it under the slightly altered name "Mullenehehownes Mill". Piers, writing a decade and a half later, added a vivid mechanical footnote. He recalled that in his time the site had contained an over-shot mill, one in which water falls from above onto the wheel's buckets, with the smallest wheel he had ever encountered; at under eight feet, roughly 2.4 metres, in diameter including its buckets. By 1682, he noted, it had been converted to a breast mill, a type where the water strikes the wheel at roughly axle height rather than from above. Two other mills on the same stretch of the Brosna were also noted by Piers, one of which was probably a tucking mill called Francis's Mill, used in the processing of woollen cloth.