When did personalizing jewelry become popular? My guess is probably in the 1960's when imagination started taking flight, and innovative uses of materials and forms became popular.
Sterling silver also became popular at that time.
Personalized jewelry tells your story in a beautiful way. Keeping cherished ones close to you, and turning an ordinary jewelry piece into a cherished memory.

However it happened, now there are many many ways to personalize your jewelry. One  most popular personalized jewelry items are Mothers bracelets.

And there are many designs to choose from! Many use lettered beads ,and you can spell out a sentiment or name.
There are beaded name bracelets with alphabet beads.
Still others use the birthstones of family members
Birthstone jewelry is a very popular style.

 New on the scene are sentiment tags. These are generally steel tag with a nice personal message  engraved in it.

Jewelry in this style started with medical alert jewelry, and is now extending farther into other areas, such as expressing personal sentiment.
One great example of this are the "Mommy Tags" business of Kirsten Reed. 

New Cameo styles are also on the rise. They are not as personalized, but the new cameos convey a sentiment and feeling in an inspired, artistic way.Some beautiful ones that I found are a mother caressing her baby.

Hope this helps!

My Lampwork Beads