Shakespeare and Language

The last hundred odd years have seen the greatest shift in culture, technology and language arguably since the beginning of written language.  With this change, languages have evolved and mutated, sometimes within years ,  the meanings of words shifting with generations. One example of such a word is gay. If we look at its original meaning and associations, for example in Shakespeare's Richard II the usage is obvious in its referencing fun, cheerful, colourful, even exciting clothing, compared with that of a poorer person.
"My gay apparel for an almsman's gown" (1595, 3.3:1791)

By the late 1890's the term had an overall tinge of promiscuity, and in the late 1940's the term began to appear in psychological writing such as the Rorschach Research Exchange and Journal of Projective Techniques, published in 1947.

Since then, the word entered use in mainstream English and has been recognized as having several meanings in dictionaries. Now in the 21st century, with the advent of the internet, overuse of the word gay has shifted its meaning yet again, mostly among the youth, though it still retains its homosexual meaning. The present use, usually used to describe objects or events in slang indicates something rubbish or stupid, as in "that bike is gay".

Reference  

Shakespeare, S. (1595) Richard II. Edited by Wright, W.A. Cambridge: Macmillan and Co.