Bavin (wood) was a traditional unit of firewood, a large log.
A bavin in the 16thC was a piece of wood standardised as three foot long and two feet round.
[1] In Hampshire in the early19thC, its cost was between 6 and 15 shillings per hundred bavins.
[2] Charles Vancouver in 1813 wrote of "Bavins for heating the oven and making a sudden but transient fire".
[4] Jane Austen in 1814 complained to her sister that “My Mother’s Wood is brought in-but by some mistake, no Bavins.