1) A stone, used originally for paving; sometimes, a cobblestone.
The OED definition of this word is ‘a rounded stone … larger than a pebble’ but the earliest example quoted is from 1617 when it was used of paving stones: it was compared to ‘some other kind of small stone’. Much earlier than that it occurred in a similar context in York: 1421 Et in bulders emptis pro eodem pavimento, 14d. We are now more familiar with boulder as a word for a large block of stone but there are no examples of it used in this way from before 1800, so its premier definition may be at first surprising. Nevertheless, in bridge-building accounts it clearly referred to what we would now describe as cobbles, as in 1675 when the workmen responsible for Ilkley Bridge claimed Ł4 6s 0d for Leading of Fillinges and Boulders for paveing the Bridge. Similarly, in 1682, George Holgate was paid for leading boulders and sand for Rotherham Bridge. It may be significant that Boulder Bridge occurs twice as a place-name in south Yorkshire, in Carlton and Hoyland Swaine. The latter was spelt Buldirbrig in 1495. The word should be linked with ‘boulder-stone’ which is on record from before 1300, especially as these stones were also used for paving.