My Thoughts…
It's really a special time when a child first starts to speak. And having witnessed the first speech of so many kids, I've come to see a commonality among first word vocabularies.
Characteristics of a child's first word vocabulary often include;
Sounds that are readily produced
When attempting to facilitate first word production it’s important to always take into account a child's sound vocabulary. Many kids really do have an innate sense of what sounds they can and cannot say and for reasons best known to them they will just clam up when asked to say something new. Often first words start/play off early developmental speech sounds (M, B, P, D, O, AH, E, I, OO)
Generally single syllable with some two syllable words
When asking for words, a child's ability organize sounds into syllables should be considered. It's important to look for sounds and words you think a child has a chance to say. When speaking to parents I often refer to this as "stacking the deck". You always want a child to succeed. This helps build confidence which in turn often leads to new sound and word ventures. Confidence is everything when it comes to first word production – or any speech goal for that matter.
Words that occur often or present a special importance
Kids form relationships with people and things around them. Kids tend to say words that have a special meaning e.g. mom, dad, bottle, Elmo, cookie etc. Who's important, what's important are good things when considering first vocabulary words.
JJ M.A. CCC-SLP