Some scholars say the word means ‘to fill’. Others say ‘fill again’. Here’s a little breakdown - from the Bible Lexicon results:
http://www.blueletterbible.org/lang/lexicon/lexicon.cfm?Strongs=H4390&t=KJV#
Don’t know if this answers your question(s) or not, Geo. There are a lot of studies on this - as others find the word ‘replenish’ as a puzzling word, too.