How does a signature develop?

In English, unlike in many other languages, signatures are typically very different from ordinary handwriting. A signature will often display all kinds of wild flourishes and elision of forms and what have you. A person usually starts out writing their name in print or in cursive, and develops the style of their signature over time.

But how exactly does a signature develop? How did mine go from a shaky, juvenile cursive rendition of "Jonathan William Purdy" to something that looks more like "Joth Wm Pdy"? (And then only if you turn your head and squint.)

Mainly I'm looking for research articles, books, and online resources on which strokes and series of characters can be elided, and what flourishes are common and allowable. This is a broad topic, and though I have a pretty clear concept of what I'm looking for, I'm finding difficulty describing it. Please ask any clarifying questions that come to mind.

First I thought about what to write. Both of my full names? That's too long... being a CS person I settled on first initial and last name. Then I just wrote it out in cursive. I kept writing it out in cursive... at first I wrote it neatly, but then I got lazier and lazier. Nowadays, I realize that almost never is a signature actually looked at, so I lose interest around the fourth letter and just make some random scribbles.

I assume other people go through a similar process?

A signature (from Latin signare, "to sign") is a handwritten (and sometimes stylized) depiction of someone's name, nickname or even a simple "X" that a person writes on documents as a proof of identity and intent. The writer of a signature is a signatory. Similar to a handwritten signature, a signature work describes the work as readily identifying its creator.

Mostly signatures are used because it is use as identity entity. Different people use different signatures and it is up to the person to decide how his/her signature should be. Normally there is no rules, but it must be unique. Nowadays signatures are not reliable, but optional methods such as fingerprints, voice identifications used.