next to, beside, near, a suffix (or postposition) often found in place names (see Karttunen)
IPAspelling:
-nɑkɑstɬɑn
Frances Karttunen:
-NACAZTLAN compound postposition next to, beside, near / junto a él, a lado de, proximidad (Z) [(1)Tp.132, (4)Zp.74,75,103,160]. See NACAZ-TLI, -TLAN. Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 156.