Gnome (monster class)
Gnomes are a class of monsters that are usually found in the Gnomish Mines. Those other than gnomish wizards are generated with 3-14 darts, a crossbow and 3-14 bolts, a bow and 3-14 arrows, 3-5 daggers, an aklys, or nothing. The probability of getting nothing is 36% for a gnome king, 50% for a gnome lord, and 64% for ordinary gnomes.
Gnomes have a chance of getting a single candle, 1/20 if in the Gnomish Mines when the level was generated, and 1/60 otherwise. The candle will be tallow 3/4 of the time, or wax otherwise. If generated on a dark level, the candle will be lit. 
In general, gnomes are not usually considered to be a big threat, especially on their own. However, large groups and the stronger versions can pose a challenge, particularly to a low-level adventurer taking on the Mines early.
A gnomish wizard is a gnome dressed up as a wizard. Most of the time, its spell attempts will fail ("The gnomish wizard points all around, and curses"), so they can easily be hit or killed by any other means. When the spells succeed, you can suffer stunning, or a splitting headache.
SLASH'EM features more gnome variants: Powerful gnome warriors, fast and cunning gnome thieves and deep gnomes in the deeper part of the mines, as well as unique gnome king, Ruggo, in the very bottom, who has his own lair. Regardless, none of these are particularly tough.
dNethack has separate growth chains for male and female monsters. Female gnomes will grow up into gnome ladies and gnome queens instead of female gnome lords and gnome kings.
... And then a gnome came by, carrying a bundle, an old
fellow three times as large as an imp and wearing clothes of
a sort, especially a hat. And he was clearly just as frightened
as the imps though he could not go so fast. Ramon Alonzo
saw that there must be some great trouble that was vexing
magical things; and, since gnomes speak the language of men, and
will answer if spoken to gently, he raised his hat, and asked
of the gnome his name. The gnome did not stop his hasty
shuffle a moment as he answered 'Alaraba' and grabbed the rim
of his hat but forgot to doff it.
'What is the trouble, Alaraba?' said Ramon Alonzo.
'White magic. Run!' said the gnome ..
[ The Charwoman's Shadow, by Lord Dunsany ]
"Muggles have garden gnomes, too, you know," Harry told Ron as
they crossed the lawn.
"Yeah, I've seen those things they think are gnomes," said Ron,
bent double with his head in a peony bush, "like fat little
Santa Clauses with fishing rods..."
There was a violent scuffling noise, the peony bush shuddered,
and Ron straightened up. "This is a gnome," he said grimly.
"Geroff me! Gerroff me!" squealed the gnome.
It was certainly nothing like Santa Claus. It was small and
leathery looking, with a large, knobby, bald head exactly like
a potato. Ron held it at arm's length as it kicked out at him
with its horny little feet; he grasped it around the ankles
and turned it upside down.
[ Harry Potter and the Chamber of Secrets, by J. K. Rowling ]