The names are simply how people referred to them for convenience-- and at the time, the shorthand isn't ambiguous. Later, of course, as treaties accumulated, there's occasionally a need to disambiguate two "Treaties of Paris", but in most cases its clear from context. . . but that's not actually their formal title.

So "The Treaty of Versailles" is typically understood to refer the 1919 Treaty; but that isn't actually its name.

The actual name is

"The Treaty of Peace between the Allied and Associated Powers and Germany, the Protocol annexed thereto, the Agreement respecting the military occupation of the territories of the Rhine, and the Treaty between France and Great Britain respecting assistance to France in the event of unprovoked aggression by Germany. Signed at Versailles, June 28th 1919"

Similarly, the actual title of what we usually call the "Treaty of Paris of 1783" (ending the Revolutionary war between Britain and the American colonies) is "The Definitive Treaty of Peace 1783"

For the people for whom these things are important -- diplomats and statesmen, international lawyers-- there are large compendia of international agreements entered into, a bit like law books. So you'll find that the Department of State annually publishes a volume Treaties in Force and the Library of Congress similarly has a complete listing of US treaties (unlike the State Department list, the LOC version has obsolete and superseded treaties as well as those in force).

Generally speaking, legal documents don't really have "names" -- they just have a title describing what the document is "An Agreement for Allocating Certain Tax Preference items between Oldco and Spinco, signed May 18th 2020 in New York" -- which will get some shorthand like the "tax sharing agreement" that's understood only in context. Treaties are much the same, they don't get real names. Lately there's been a fashion for giving new laws some catchy name -- "the Ryan White Act", and so on . . . this wasn't past practice either for laws or treaties.