The traditional form 總 shows silk threads being tied into one bundle. Gathering all strands together gives 'total'; what holds for the whole gives 'always'; the one who holds the bundle is the chief.
总是 always, 总统 president ('chief unifier'), 老总 the boss. 总之 'in short' wraps any rambling explanation. Every company's CEO is a 总 — 张总, 李总: Chief Zhang, Chief Li.
All threads TIED into one bundle — the TOTAL, held ALWAYS by the CHIEF.
In Chinese offices the surname + 总 (王总 'Chief Wang') is the default honorific for any boss — one character doing the work of 'CEO'.