Not exactly an object 'inside' the kernel, but I was recently caught out by the fact that /proc/net/snmp doesn't have much to do with the SNMP protocol. Rather it tracks socket statistics for IP, ICMP, TCP, and UDP, and is one of the sources of information for the netstat utility.

My recent venture in the filesystem have been somewhat fun. The problem isn't so much misnamed objects, and more that the kernel is filled with seemingly undocumented, arcane, old things. `sb_bread` isn't some kind of food, but the "SuperBlock Buffer Read" method, and `brelse` means "Buffer Release" (and not, somethingsomething else, as I initially thought).

BH means Buffer Head. The meaning and usage of Buffer Head has changed a lot across Linux versions. It's the basic unit of IO operations, but nowadays most users would use a bio for most of what you would have used a buffer head in the past. When you're working on filesystems you'll have to use BHs to talk to the hard drive though.

Linux FS infrastructure and Ext2 share a lot of names. For instance, ext2 and linux both have superblocks, inodes, blocks, etc. They are... logically the same, but at the same time they're very different - one lives purely on the disk, the other provides functions to the kernel. This makes conversation very complicated, when talking about the superblock, you have to mention which superblock you're talking about, because that's not always obvious from context.