What does the suffix “-saurus” mean?

They have different origins:

thesaurus ORIGIN late 16th cent.: via Latin from Greek thēsauros ‘storehouse, treasure.’ The original sense [dictionary or encyclopedia] was narrowed to the current meaning by the publication of Roget's Thesaurus of English Words and Phrases (1852).

tyrannosaurus ORIGIN modern Latin, from Greek turannos ‘tyrant’ + sauros ‘lizard,’ on the pattern of dinosaur.

From NOAD.

So, obviously, they do not have the same meanings. Although some people do like to make jokes about this. Cf. What's a big-vocabulary word for someone with a big vocabulary?

According to Wikipedia, thesaurus derived from Latin and meant “treasure store”. So assuming the first half of the word is treasure, then saurus must mean store presumably.

Contrarily, tyrannosaurus derived from the roots tyrannos and sauros from Greek, which meant “tyrant lizard”.

Therefore, since one derives from Latin and the other from Greek, I would assume the similarities in the roots are purely coincidental.

As was mentioned in another comment, one interpretation of the Greek word thesaurus is "hoard". That interpretation made me think of "dragon's hoard". If saurus = lizard = dragon, that could be the link between the -saurus- root and thesaurus. Saurus is the dragon/lizard, and thesaurus implies the dragon's hoard.

If there is a sililarity in words, the passage of time can change the meanings and sounds of words. As noted above hoard and treasure translate to the word thisavrós in Greek. But this does this does not sound (IMO) like the word thesaurus (using Gogle translate).Thisavros has a potential suffix that sounds similar to sávra: Greek word for Lizard.

Accoding to (https://www.youtube.com/watch?v=nnmcNPU4Hks) the ancient Egyptian God of words/writing is Thoth/ Djehuty. The lengthy sound ...Deeeeeee.... is said to originate from the sound made by an eagle swooping down from the sky/sun.The sun, back then, was worshiped as God and thus early man adopted the sound. Djehuty seems to have changed to Deus in Latin and Theos/Theou in Greek - the word for God.

Joining 'Theos' with 'Savros' creates a God-Lizard, a Theosavros. In addition the words 'Savvy and savoir, the latter being French for to know, are closer to the sound of the Greek sávra. In the King James Bible John 1:1 the verse reads: In the beginning was the Word, and the Word was with God, and the Word was God. Currently, the Thesaurus is described a collection of and knowledge of (God's) words.

Google's etymology of the word savant indicates an 'old' French origin of savoir or saveir, which itself originates from the Vulgar Latin *sapēre,“to taste”. Thus using Google translate we have God, Knowledge (tree),wisdom and taste. Also, evil and apple share the word malum in Latin.

Alternatively, in Egypt, the snake symbol, or Uraeus, located on a Pharaoh’s headdress denoted great wisdom and God-like powers. Also, just about every religion around the world starts with a snake or serpent deity - See Nagas in India. These have gone on to morph into dragons:(Dragons, Serpents and Slayers, Daniel Ogden, 2013, and; https://en.wikipedia.org/wiki/Snake_worship. The Thesaurus literally becomes a book for the wisest: as equated with virtues of the snake, lizard or serpent.

Also, dragons,as dramatised in the film Jason and the Argonaut (with the Hydra), or as in the Garden of Hesperides guarding orchards with one apple tree were also described as protecting hoards of gold and treasure (in ancient times). The film shows one such treasure: a Golden Fleece. Others believe dinosaur fossils, which gave rise to the many fantastic legends, and precious metals and stones were often found together at a time when little was known about dinosaurs.

All information is from older books read over the years.

Update: Albanian word for Treasure is Thesar

A collection of valuable things. Etymology: From tresor, from thesaurus, from θησαυρός. But, maybe from Albanian Thesar, "thes" (sack) and "ar" (gold). Any single thing that one values greatly. Sack of gold?

Sounds more plausible as a description of treasure than thisavrós

Also, since the nineteenth century, both countries have been separate nation-states, but for at least twenty-two centuries Albania and Greece belonged to the same state in various forms that it took (https://www.google.com/search?client=firefox-b-d&q=was+albania+part+of+greece).