<tre> 'farmstead' + <ker> 'fort' + <woles> 'lower' (Note woles added to differentiate from nearby Tregear.
Historic forms:
?Walter de La Byri, son of John de La Byri 1317 (N.A. - AR/1/331)
Berry downs 1734 (CRO AD103/84)
Berry Lane 1871 (Will of Richard Fowler)
Berry Lane 1989 (Douglas, 1989)
Berry Lane Farm 1989 (Douglas, 1989)
Berry Farm 2014 (OS 2014)