Here's why:
* Nomenclature: Restriction enzymes are named based on the bacterial species from which they are isolated. The first three letters of the name represent the genus and species of the bacterium, followed by a Roman numeral indicating the order of discovery from that source.
* HindII's Discovery: The enzyme HindII was isolated from the bacterium *Haemophilus influenzae* Rd, the second restriction endonuclease discovered from this species.
Therefore, the name HindII reflects its order of discovery from *Haemophilus influenzae* Rd, not an arbitrary numbering system.
