Capitonym

A capitonym is a word that changes its meaning (and sometimes pronunciation) when it is capitalized, and usually applies to capitalization due to proper nouns or eponyms. It is a portmanteau of the word "capital" with the suffix "-onym". A capitonym is a form of homograph and — when the two forms are pronounced differently — also of heteronym. In situations where both words should be capitalized (such as the beginning of a sentence), there will be nothing to distinguish between them.

Although some pairs, such as "march" and "March", are completely unrelated, in other cases, such as august and catholic, the capitalized form is a name which is etymologically related to the uncapitalized form. For example, "August" derives from the name of Imperator Augustus, who named himself after the word "augustus", whence English "august". And both "Catholic" and "catholic" derive from a Greek adjective meaning "universal". Pairs in which one word is simply a secondary meaning of the other — e.g. "Masonry" (secret society), which is essentially a peculiar use of the word "masonry" (wall building) — are omitted.

In other languages there are more, or less, of these pairs depending on that language's capitalization rules. For example, in German, where all nouns are capitalized, there are many pairs, such as "Laut" (sound) ~ "laut" (loud) or "Morgen" (morning) ~ "morgen" (tomorrow). In contrast, in Italian, as well as Spanish, almost no words (except proper names) are capitalized, not even months, weekdays nor ethnical adjectives, so there are extremely few, if any, such pairs. (An example is "Messa" (Mass) ~ "messa" (feminine past participe of "mettere" = to put), though the former is sometimes spelled with a lowercase "m" too.)

Some question the correctness of certain case-sensitive distinctions that others make. Examples are "church" (a building) and "Church" (an organization), "mass" (physical quantity) and "Mass" (liturgical function). In the Soviet Union, it was forbidden to write "God" with an upper-case letter, making impossible this manner of distinguishing "God" (the being believed to create and rule the universe) from "god" (one of beings believed to control some part of the universe). [http://www.airpower.maxwell.af.mil/airchronicles/aureview/1972/nov-dec/clark.html]

Examples in poems

The following poems, of unknown origin, are examples of the use of capitonyms:

Job's Job In August, an august patriarch Was reading an ad in Reading, Mass. Long-suffering Job secured a job To polish piles of Polish brass.

Herb's Herbs A herb store owner, name of Herb, Moved to a rainier Mount Rainier. It would have been so nice in Nice, And even tangier in Tangier.