Titan, means a person of great size, strength, intelligence or importance (Oxford Advance Learner's Dictionary).
In wikipedia:
https://en.wikipedia.org/wiki/Symphony_No._1_(Mahler)
Your guide to listen to Mahler's symphony No. 1:
https://www.youtube.com/watch?v=RqRiG5KW11g
Mahler's symphony No. 1 is also called symphonic poem (p. 540, D. M. Randel, the Harvar Bigraphical Dictionary of Music).
He wrote this symphony at his twenties.
