summer (n.1)

early 15c., "supply for future use; collective wealth;" mid-15c., "sum of money set aside for a specific purpose;" Middle English developments of stock (n.1), but the ultimate sense connection is uncertain. Perhaps the notion is of the "trunk" from which gains are an outgrowth, or from stock (n.1) in obsolete sense of "money-box" (c. 1400). Probably several different lines of development are represented here.

The meaning "subscribed capital of a corporation" is from 1610s. The figurative phrase take stock in "repose confidence in, regard as important" is from 1870, from the notion of investment.

In stock "in the possession of a trader" is from 1610s. The meaning "broth made by boiling meat" is from 1764. As "raw material from which anything is made," 1873, especially in reference to paper.

Theatrical use, in reference to a company regularly acting together at a given theater, performing recurring types, or staging a fixed set of plays, is attested from 1708, from the notion of something habitually produced or used. 

Taking stock "making an inventory" is attested from 1736. One's stock in trade in a literal sense was "goods kept on hand by a dealer or storekeeper" (1760s) with figurative use by 1784.

As the collective term for the movable property of a farm, especially horses, cattle, sheep, and other useful animals, it is recorded from 1510s; hence livestock, stockyard. "The application to cattle is primarily a specific use of the sense 'store', but the notion of 'race' or 'breed' ... has had some share in its development" [OED].

early 14c., sommen, "to count (things, people), count up, calculate, combine into a total," from Old French sommer "to count, add up," or directly from Medieval Latin summare, from summa (see sum (n.)).

The meaning "briefly state the substance of" is recorded by 1620s (since c. 1700 usually with up). Related: Summed; summing.