Hi Amme- can you describe the liquid soap you bought, i.e., is it a 'true' Castile liquid soap made with nothing but water, olive oil and KOH? If so, is the smell a rancid smell, or is it something not actually rancid, but rather 'distinctive', like a fresh fatty/oily soapy smell?
I ask, because I find olive oil gives off a fresh fatty/oily soapy smell in my (unscented) handmade liquid soap. Many folks that make their own liquid soap report the same kind of smell from olive oil, especially the virgin kind, in their unscented liquid soap (and bar soap as well). For what it's worth, the most olive oil I use in my liquid soap formulas is 65% worth.
Anyway, to me it's not an unpleasant smell because it reminds me of my happy childhood days and the unscented olive oil liquid soap my kindergarten always stocked in their bathroom soap dispensers.
I make mention of all the above just in case you go into making your own liquid Castile soap with the expectation that it won't have any kind of scent at all in its natural, unscented state, only to become disheartened when you find that it does (and it will). No worries, though- the natural smell is easily covered over with either FOs or EOs. At least mine is anyway. I normally use FO at a rate of 1% as per the total weight of my finished, diluted soap and it totally covers up the natural smell.
Here are some threads I found about the natural scent of unscented handmade liquid soap:
https://www.soapmakingforum.com/threads/my-cp-liquid-castile-soap-has-a-soapy-smell.70048/
https://www.soapmakingforum.com/threads/weird-rancid-smell-in-ls.61482/
https://www.soapmakingforum.com/threads/the-smell-of-liquid-castile-soap.60453/
IrishLass
