The word 'God' comes from the same Germanic root as the words 'gold' and 'good.' This word generally applies only to a divine being, specifically the Supreme Being who created all things. It is sometimes used to refer to lesser beings or even human beings, such as describing a mythological being such as Apollo as the god of healing. But Paul said that there is only one true God and all others are only 'so-called gods' (1 Corinthians 8:5).
The word 'lord' is an old English word meaning one who rules over others. This word can be applied to God or to a human being. For example, England used to have lords who ruled over various jurisdictions. Around 300 BC, the Jews stopped pronouncing the name of the God of Israel and instead began using the term Adonai (which means lord in Hebrew). When the Old Testament was translated into English, the translators used the word LORD (in all capital letters) wherever the Hebrew text used the proper name of God (YHVH, Yahweh). This was out of respect for those who believed the name of the God of Israel should not be uttered. In the New Testament, wherever an Old Testament passage containing this name is being quoted, the Greek text uses the word kurios (which is the Greek word for Lord). What many people fail to understand is that the name Jesus is the fulfillment of the name Yahweh and constitutes the fully revealed proper name of the God of Israel. Yet many who refuse to utter the name Yahweh will freely speak the name Jesus. Who can figure!