This is the 4058th most frequent Russian word.
мурашко
The Russian word "мурашко" is a diminutive form of "мурашка," which colloquially refers to a tiny ant or to "goosebumps" in a figurative sense.
In this sentence, 'мурашко' metaphorically represents a 'shiver' or a sensation caused by the cold.
По спине пробежал мурашко от этого ледяного ветра.
A shiver ran down my spine from the icy wind.
'Мурашко' here is used as a proper noun, likely a surname.
Он стал мэром города и решил построить парк имени Мурашко.
He became the mayor of the city and decided to build a park named after Murashko.
The word 'мурашка' (a small ant or insect) forms the base here, creatively interpreted by the children.