A couple months ago, something I was reading referred in a footnote to an extended note by Joyce Baldwin in her Zechariah commentary on jealousy. Baldwin's discussion was excellent, as her work usually is, but one thing stood out. I'll quote the two relevant paragraphs and then comment further. Some of the formatting on her Hebrew transliterations isn't exact, but I've tried to do the best I could with the tools at my disposal.
The Hebrew word qin'a is translated in RSV by 'jealousy', 'zeal', and 'fury'. Its root is probably connected with an Arabic word meaning to become intensely red (or black) with dye, and so by derivation it draws attention to the colour produced in the face by deep emotion. The Greek zeloo, 'to be jealous', derived from zeo, 'to boil', also expresses deep feeling. From it the English words 'zeal' and 'jealousy' are both derived, so indicating that the emotion can be directed to good or bad ends. When it is self-regarding it results in intense hatred, but when it is concerned for others it becomes a power capable of accomplishing the most noble deeds.
It is significant that God is first spoken of as 'jealous' at the giving of the covenant code (Ex. 20:5; 34:14; Dt 5:9), when the special relationship was established between the Lord and His people, Israel. Because they are His, they can belong to no-one else, hence the prohibition of idolatry and the sanctions against it in the third commandment; but these are followed by assurances of 'steadfast love to thousands of those who love me and keep my commandments' (Ex 20:6). God's jealousy is a measure of the intensity of His love towards those with whom He has entered in covenant. So great is His love that He cannot be indifferent if they spurn Him by disobedience or sheet carelessness. [Joyce Baldwin, Haggai, Zechariah, Malachi, pp.101-102]