Given that the Arabs ruled southern Spain for about 800 years, it isn't surprising that the Arabic language influenced the local Latin dialect that eventually evolved into modern-day Spanish. Some scholars estimate that around 4,000 Spanish words have been influenced by Arabic.
While we aren't sure about the validity of all those claims ("hasta la vista" seems to be a stretch), the following nine seem to be fairly well-known.
1. Aceite and aceituna - oil and olive [زيت والزيتون]
From one Mediterranean region to another, the words stuck.
2. Alfombra - carpet [ حنبل]
The Arabs are known for their rugs.
3. Ojalá - hopefully [ إن شاء الله]
"Inshallah" is probably one of the most popular things to say in Arabic. It caught on in Spanish too.
4. Azúcar - sugar [سكر]
If you just drop the "a" at the beginning, the two words are nearly identical.
5. Ajedrez - chess [شطرنج]
It may not sound quite as similar, but linguistics point to the Arabic word as the origin of the Spanish word. It's also rumored that the term "checkmate" originates from either Arabic or Persian.
6. Fideo - noodle [ فيداوس]
With Italian pasta just nearby, we're supprised that the term for noodle was influenced by Arabic.
7. Aduana - customs [ ديوان]
Before border security was a thing, the Moors influenced the Arabic word for customs on their Spanish subjects.
8. Alcohol - alcohol [ الكحل]
Considering the relationship that some Arab cultures often have with alcohol (i.e. it's illegal), it's interesting to note that the Spanish word, which went on to influence the English word, originated from Arabic.
9. Almoháda - pillow [ المخدّة]
Where would any of us be without pillows? Native Spanish speakers owe their term for our favorite object to Arabic as well.