Curtsy and courtesy are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It suggests what word you it anticipates you want to save time. Quite often, its suggestions are more humorous than useful.
Curtsy is a noun. It means the bow women and girl subjects make towards a member of royalty.
Courtesy is a noun. It means a gesture done with consideration, showing good manners and respect.
The following story uses both words correctly:
Courtney saw an absence of manners manifesting in her generation, so she created an etiquette school in response. Entry level classes started small with table manners and basic courtesy, while higher level classes dealt with meeting dignitaries and how to properly bow and curtsy for royalty. Her students were thrilled when small changes in their approach paid off in spades at work.