1) The securing of a dam.
For centuries it was water power that drove the mills which ground our corn and fulled the weavers’ cloth, and in order for that power to be used effectively it was necessary to construct dams and weirs on our rivers which would halt or control the flow of water. The dams had to be secured on both banks and that was not a problem when they were in one man’s possession. Often though two parties were involved and only one of those stood to gain financially from the building of the dam, so agreements had to be worked out which would satisfy the prospective mill-owner and his neighbour across the river. The word used for the securing of the dam was ‘attachment’, and the evidence for that dates from the thirteenth century: a.1245 concesserunt dicto Willelmo de Percy … attachiamentum cujusdam stagni, Haggenby
1264 pro atachiamento stagni molendini de Kerbi
1301-2 de atachiamento stagni de Kildewyk. Examples in English are found regularly from the fifteenth century: 1473-4 to knytte, attache, festen and make of new another new werre and milnedame, Barnsley. In 1530, Edmund Kaye of Linthwaite in the Colne Valley wrote in his will of the fulling mill at Lees in Golcar and the attachyment of the said mylne damme opon [his] proper lande
that is the land which belonged to him. Similarly, a Barkisland title deed for Bowers Mill referred to the attachementt of a certen damme for a walkemilne in 1580. More explicitly, in 1539, the attachment of a dame at Fenay Bridge near Huddersfield was said to be jonyd, sett and festenyd in and upon … Briggerodebothome. Occasionally the word was abbreviated: 1543 Arthur Key hath given … one parcel of ground … in eschaunge for the tachement of oone milne damme in Rowley. The verb was employed less often but in 1581 an agreement between Thomas Pilkington of Bradley and John Armytage of Kirklees, whose lands lay on opposite sides of the river Calder, gave the latter the right of erectinge, buyldinge, annexing, attaching and affixing of a dam or dames … for one milne or more milnes.
2) In legal documents the verb could mean ‘to arrest’ or lay hold of a person or thing.
c.1525 caused diuers of the seruantes of your seid oratour to be attached, Sutton in Craven
1656 Abraham Woodhead … was attached to answer Elizabeth Greene, spinster, why he with James Greene did eject her from her farm, Holmfirth. The noun sometimes referred to an article seized by officials to satisfy a debt, a ‘distress’: 1689 he went away, takeing a chair with him under the pretence of an attachment, Holmfirth.