The rule you mention is House Rule XIV, which deals with decorum in debate. Clause 1 of that rule prohibits certain, but not all, references to the Senate and to Senators. The prohibition was put in place in order to avoid verbal misunderstandings which might lead to strained relations between the two chambers. While it is in order to refer to the Senate or actions of the Senate in a neutral way, it is out of order to make critical comments about the Senate or its members. Also prohibited are characterizations of individual Senators or their motivations. For example, it would be all right for a House member to say: "The Senate passed the bill yesterday with several amendments." However, it would not be appropriate to say, "After months of stalling, the Senate finally bothered to pass our bill but only after loading it up with lousy amendments."

There are several reasons for regulating mentions of the Senate and its Members. First is the tradition stated by Thomas Jefferson in his "Manual of Parliamentary Practice," which notes that in a bi-cameral system each chamber should act independent of the other, and not be influenced by the other's proceedings. At its heart, bi-cameralism encourages the check and balances that come from the differences, and not the similarities, between the two bodies.

A second Jeffersonian principle is that the relationship between the two chambers should be marked by civility and reciprocal courtesy, known as "comity." Jefferson warned that referring to proceedings in the other body might lead to a misunderstanding and a subsequent breach in the relationship between the two. The sometimes colorful history of Congress suggests that Jefferson's concern was not unfounded. On a famous occasion in 1856, a Member of the House assaulted a Senator in the Senate chamber after taking exception to words the Senator had spoken in debate. The Senator was so seriously wounded, he could not return to work for 3 years.

Although they are not required to, it has become House tradition for Members to use "the other body" instead of "the Senate," and "a Member of the other body," instead of "Senator Y." However even using such generic terminology may not suffice to meet decorum standards. The Chair may still call to order a Member who is impugning the motives of a Senator, disparaging the character of a Senator, urging the Senate to take a certain action, or characterizing an action already taken by the Senate, even if cloaked in "other body" vocabulary.

The Senate has no standing rule prohibiting references to the House of Representatives or its Members. However, the Senate's presiding officer has on numerous occasions been asked to admonish Senators making critical or disrespectful remarks about the House or House Members. A combination of self-restraint and internal policing has prevented House references from becoming a problem for the Senate. In fact, the rules of the Senate prohibit remarks in only two categories: Senators may not "refer offensively to any State of the Union," nor may they "impute to another Senator any conduct or motive unworthy or unbecoming a Senator."