It is to do with burial in wool. The Burial in Wool Acts 1667 and 1678, was legislation intended to promote the wool trade, requiring that corpses should be buried in wool. Initially the officiating priest was required to certify that a deceased person had been 'buried in wool' and later, relatives of the deceased had to swear an affidavit within eight days of a 'woollen burial.' This was recorded in the registers. Failure to comply resulted in a fine of 5GBP which was levied on both the estate of the deceased and on those associated with the burial. The acts were repealed in 1814, although long before then it had been largely ignored..
See
http://www.historyhouse.co.uk/articles/buried_in_wool.htmlThe 1678 Act stated that'.....no corpse of any person (except those who shall die of the plague), shall be buried in any shirt, shift, sheet or shroud or anything whatsoever, made or mingled with flax, hemp, silk, hair, gold or silver, or in any stuff or thing other than what is made from sheep's wool only....'
If someone was buried in linen an informer was entitled to half the fine. In consequence of half the fine going to the informant, the relatives of the deceased usually arranged that a relation or dependent should "inform" and thus secure the reward for the family.
Stan