The term remains obscure. The MED entry for tallow includes the variant form tarowe (with rhotification), but does not offer any other precedents for this Anglo-Norman spelling.
s.
1tallow, animal fat (?):
(
c.1325
) E pus pernez tarock e oynt (ms. noyit) de porck marle e pus pernez e mettez outer le fu
135.C530
tarock (c.1325)