If you are talking about one of these then I have never used anything but washer. Though where the word comes from is a mystery. The OED says it is of "doubtful origin", though they do have examples of its use since the fourteenth century.
1a. A perforated annular disc or flattened ring of metal, leather, or
other material placed between two surfaces subject to rotative
friction, to relieve friction and prevent lateral motion and
1346 Accts. Exchequer King's Remembrancer 470/17 m. 2 De..v
Cheynes pro barr[a] continentibus L. Linches, v. paribus tenellarum,
ij. Whashers [etc.].
1544 in Lett. & Papers Henry VIII XIX. i. 148 Spare wheles for
small ordynaunce 12 pair, lynce~pynnes, wasshers, [etc.].
1611 J. Florio Queen Anna's New World of Words Cérchio di ferro,
an iron hoope, amongst gunners called a washer, which serues to keepe
the iron pin at the end of the axeltree from wearing the naue.
1682 in Early Rec. Town of Providence (Rhode Island) (1894) VI. 93
Jn ye Parlor 3 Cart boxes, i lince pinn & a washer 00–01–00.
1704 Dict. Rusticum at Cart The Washers, being the Rings on the
ends of the Axle-tree.
1705 tr. G. Guillet de Saint-Georges Gentleman's Dict. ii. at Nave
It has likewise in each end of the hole, through which the end of the
Axletree goes, a ring of iron called the wisher, which saves the hole
of the nave from wearing too big.
1795 Herschel in Philos. Trans. (Royal Soc.) 85 371 It is keyed
fast at C; with proper washers between the joints to allow of a very
1805 R. W. Dickson Pract. Agric. I. Plate xii Every tooth screws
through a double frame separated by iron washers for greater
1847 R. Brandon & J. A. Brandon Anal. Gothick Archit. I. 102 The
closing ring or door latch..[consists of] the flat plate or washer,
fixed to the outer surface of the door; the handle or ring; and the
1872 O. W. Holmes Poet at Breakfast-table i A washer..makes a
loose screw fit.
1876 R. D. Blackmore Cripps xxvi The vast diversity of wheels, as
well as their many caprices of wagging, according to the state of