Found in the spellings of Atkinson, Aitchison, Acheson, Aicheson, and Aitcheson, it is as a patronymic form of the medieval male given name Atkin or Adkin, itself a double diminutive of the Hebrew name 'Adam', meaning 'red earth'.
But for natural conception, age rarely keeps women from getting pregnant until they are over 40. Even in their early 40s, though, most women are still able to get pregnant, especially if they use ovulation prediction.
If you stop nursing at a time when your body is used to producing copious amounts of milk on a routine basis, such as with a young baby who nurses eight to 12 times a day or a baby going through a growth spurt, it takes your body a longer period of time to decrease and ultimately stop producing milk. If you stop nursing at a time when your body isn't producing a lot of breast milk, such as with an older infant or toddler, your body adjusts more quickly. The ultimate time line depends on your body; there is no one-size-fits-all time line for letting your milk dry up.