You mean like
let func = "do_something" in
The above itself is not possible, but you can achieve something similar by putting functions in a map-like (dictionary) structure and indexing them by their names, e.g.
let () =
let funcs = [ "do_something", fun () -> print_endline "Doing something" ] in
try (List.assoc "do_something" funcs) ()
with Not_found -> print_endline "Could not find function"