One of my partners recently asked whether the correct suffix is -ory or -ary when referring to a bank in a deposit account control agreement.  The word "deposit" is derived from the Latin words de and ponere, meaning down and place, respectively. 

The noun suffix -ory derives ultimately from the Latin -orius and generally means "characterized by" or a "place for".  Thus, a laboratory is a place for work.  If you think of the bank as a place, you might be inclined to refer to it as a "depository bank".

The noun suffix -ary also derives from the Latin -arius and generally means "connected with" and "a person engaged in".  Thus, a notary is a person engaged in making marks or notations.  If you think of a bank as engaging in taking deposits, then you might be inclined to refer to it as a "depositary bank".

The foregoing etymological discursion, however, doesn't really answer the question decisively.  Can it be claimed with confidence that either spelling is ineluctably correct?  The Commercial Code sides with "depositary bank", a term that it actually defines in Section 4105(2) and uses in numerous other statutes.  That being said, the legislature embraces diversity by using the term "depository bank" in other codes, including the Code of Civil Procedure, the Corporations Code, the Family Code, the Government Code, the Insurance Code, and the Revenue and Taxation Code.

Don't get me started on advisor versus adviser.