The names of VOPs that implement functions are based on the function name. Other VOPs may use any base that doesn't conflict with a function name. There are some rules used to obtain the base name for related operations.
To get the name of a setting operation, replace the string "ref" in the name with "set". If "ref" doesn't appear in the name, add the prefix "set-" to the base name. For example, svref becomes svset, and symbol-value becomes set-symbol-value.
To get the name of a conditional VOP from the name of a predicate, add the prefix "if-" to the predicate name. For example, eq becomes if-eq. eq by itself would be a VOP that returned true or false value.
Some operations check for some error condition, magically signalling the error through an implicit control transfer. These operations are prefixed with "check-", as in check-fixnum and check-bound.