The help text in 'command.txt' for "Fire an item" appears to be mostly "Throw an item" (e.g. much of it is inaccurate).
Code:
Fire an item (f) or Fire an item (t)
You may throw any object carried by your character. Depending on
the weight, it may travel across the room or drop down beside you.
Only one object from a pile will be thrown at a time. Note that
throwing an object will often cause it to break, so be careful!
If you throw something at a creature, your chances of hitting it
are determined by your pluses to hit, your ability at throwing,
and the object's pluses to hit. Once the creature is it, the
object may or may not do any damage to it. You've heard rumors
that some objects found in the dungeon can do huge amounts of
damage when thrown, but you're not sure which objects those
are.... Note that flasks of oil will do a fairly large chunk
of damage to a monster on impact, supposedly representing fire
damage, but it works against fire elementals too - not that it's
exactly worth it by that stage of dungeon exploration. If you are
wielding a missile launcher compatible with the object you are
throwing, then you automatically use the launcher to fire the
missile with much higher range, accuracy, and damage, than you
would get by just throwing the missile. Fire or Throw requires
a direction. Targeting mode (see the next command) can be invoked
with "*" at the "Direction?" prompt. This command takes some energy.