Larvitar in depth
Yōji, kirai, saurusu
The Japanese name, ヨーギラス (Yogiras), breaks down into three parts: 幼児 yōji (small child) or 幼生 yōsei (larva), 嫌い kirai (hated) and ソーラス sōrasu, a distortion of サウルス saurusu, the suffix -saur. The ending is the signature of the whole family and reaches Tyranitar without changing.
English, which is also the name we use in Spanish, mixes larva with tar, building on the popular—false—idea that oil and tar come from dinosaurs. French took another route and came out better: Embrylex combines embryon with silex, embryo and flint.
The design draws on dinosaurs and kaiju, the two obvious references. Less obvious is its habit of devouring mountains, fences and anything else that gets in its way, which recalls the Tarasque, the man-eating monster from Provençal legend.
Level 30 comes too soon
There is a trap here that is worth spotting before you fall into it. Its level-up move list keeps growing long after the evolution point: Earthquake at 31, Stone Edge at 33, Thrash at 36, Sandstorm at 39 and Hyper Beam at 42. Since it evolves at 30, it learns none of those six as Larvitar unless you cancel the evolution manually, several times in a row.
Playing normally, then, the strongest move it gets is Crunch at 27, with Rock Slide from 15 and Stomping Tantrum from 18 as attacks of its own types. That isn't much for the middle stretch of a playthrough, and it explains why many trainers leave it in the box and only bring it out once it is a Pupitar. The other option, leaving it unevolved until 33 to get Earthquake and Stone Edge as standard, delays level 55 even further.
Its stat spread doesn't help with improvising either. With 45 Special Attack, there is no way to make use of Earth Power, Dark Pulse or Noble Roar, all of which are on its TM list; everything it does has to go through the physical side.
Sand Veil and other small print
Its second Ability, Sand Veil, raises its Evasion during sandstorms and arrived as a Hidden Ability, meaning it wasn't available in the first two generations in which the species existed. It makes sense thematically—sand, rock, mountain—and has little practical use at the first stage, where what it lacks is durability, not dodging. It learns Sandstorm by TM and also at level 39, if it manages to get that far without evolving.
Another archival detail: between Diamond and Pearl and Platinum, they changed its sprite animation but not the static sprite. It's the kind of tweak you only notice when comparing both versions at once.
The Mt. Silver Egg
In the animated series, it had a bigger role than pre-evolutions usually get. Ash hatched one from an Egg given to him by Professor Elm in Hatch Me If You Can, with instructions to return it to its mother, who lived on Mt. Silver. That Larvitar froze with embarrassment whenever anyone other than Ash or Pikachu came near it, and didn't stop until Mother of All Battles, the reunion episode.
It wasn't its first appearance overall: it had appeared earlier in the short Pikachu's PikaBoo, refusing to play hide-and-seek because it had to watch over a garden. And in Pinch Healing, another one appears, just as shy, responding with Sandstorm every time someone approached it head-on. Three appearances, three versions of the same personality: an animal that spends its childhood underground and has no idea what to do when people look at it.