"Little Endian" means that the low-order byte of the number is stored in memory at the lowest address, and the high-order byte at the highest address. Intel processors (those used in PC's) use "Little Endian" byte order.
"Big Endian" means that the high-order byte of the number is stored in memory at the lowest address, and the low-order byte at the highest address. Motorola processors (those used in Mac's) use "Big Endian" byte order.
BIG ENDIAN refers to data
ordering where the most significant portion of an operand is stored at the lower address. LITTLE
ENDIAN refers to data ordering where the most significant portion of an operand is stored
at the higher address.
I strongly suggest that you should read the wishbone spec, which explain this very clearly!