The Collaborative International Dictionary of English v.0.48:

Tot \Tot\, n. [Cf. Toddle, Tottle, Totter.]
   1. Anything small; -- frequently applied as a term of
      endearment to a little child.
      [1913 Webster]

   2. A drinking cup of small size, holding about half a pint.
      [Prov. Eng.] --Halliwell.
      [1913 Webster]

   3. A foolish fellow. [Prov. Eng.] --Halliwell.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tot \Tot\, n. [L.]
   Lit., so much; -- a term used in the English exchequer to
   indicate that a debt was good or collectible for the amount
   specified, and often written opposite the item.
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Tot \Tot\, v. t. [imp. & p. p. Totted; p. pr. & vb. n.
   Totting.]
   1. To mark with the word "tot"; as, a totted debt. See Tot,
      n.
      [Webster 1913 Suppl.]

   2. [Cf. Total.] To add; to count; to make up the sum of; to
      total; -- often with up. [Colloq., Eng.]

            The last two tot up the bill.         --Thackeray.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

tot
    n 1: a small amount (especially of a drink); "a tot of rum"
    2: a young child [syn: toddler, yearling, tot, bambino]
    v 1: determine the sum of; "Add all the people in this town to
         those of the neighboring town" [syn: total, tot, tot
         up, sum, sum up, summate, tote up, add, add
         together, tally, add up]